# Walnut F1



## Ivan TT (Aug 22, 2017)

Balanced Version= With 2.5mm Balanced out Interface and still have 3.5mm interface
Standard Version= Only have 3.5mm interface

WARNING! F1 is designed to drive high-impedance earphones, essentially set to what is high-gain mode on other amps. This leads to distortion (when using 3.5mm se out) or extremely high output level (when using 2.5mm balanced output).  Solution is in post #9.
https://www.head-fi.org/threads/walnut-f1.858439/#post-13674030

Tip:
If you have 2.5mm earphones, you can plug the output of your DAP or phone into "Power out" socket. This will utilise balanced output buffers only, bypassing opamp and volume control altogether. See post #17 for details.
https://head-fi.org/threads/walnut-f1.858439/page-2#post-13675934

1. Interface: 3.5MM or 2.5 interface
2. Output power:300mW
3. Operational Amplifier Chips Model: OPA2134
4. SNR: 90DB
6. Lithium battery capacity: 1500MAH
7. Charging Interface: Standard MICRO USB.
Package:

1 X Headphone Amplifier(*earphone not include*)
1 X Charging Cable
1 X AUX Cable
2 X Silicone straps







Walnut F1 amp size is small, 80 * 50 * 20mm than a bank card is slightly smaller, but the small head also has great wisdom, this section of the sound of the amp should be said that the bile is more foot, simply is the sound more sweet The Plus after the amp; Can feel out the sound field is significantly large, opener is the original BB of the OPA2134. Sound characteristics in general are warm and delicate type, strong driving force, "bile". Low-frequency quality and quantity. At the same time 2.5mm version with a balanced output, balanced output has been applied to professional recording field, balanced output is characterized by high degree of separation, the thrust is about twice the power output.








operational amatement OPA2134, OPA2134 is designed for audio and designed for the op amp, sound mellow, rounded, neutral warm, bile is very strong, is known as the most electronic tube audio amplifier. Feeling like the upgraded version of 5532, all aspects have greatly improved, good resolution, music taste better, there is bile, the sound is relatively thick and a bit rigid, comprehensive quality is very good. Especially for music performance.
The amp can be replaced by the op amp. Direct plug design. Is now the mainstream design, different op amp to bring a different tone.





















Almost completely using the machine's power supply circuit, up to 24V (+12 V gnd -12V) of the pressure, easy to control the various types of op amp on the market, the strength of the launch of the loud field. While supporting the side of the charge while listening to music.








Power supply part of the selection is 24v 1A power supply, ripple very small (using the commonly used three-terminal regulator 78M12 79M12, under normal circumstances no noise at the end), the filter capacitor is Ina vr series and gold fw series of high-quality capacitors The Imported high current full-shielded inductors.

(16 ohm-400 ohm), and due to the high supply voltage, long-term use of the shell will be a slight signs of fever (not more than 30% of the use of a class of current amplification and op amp voltage amplification, degree).

The use of 3.7V high-capacity lithium battery-powered, boost to 24v maximum current 1A, battery capacity 1500mah, life 4 to 5 hours or so. When charging the use of Andrews can be a common charging line. Do not use when charging. Charging time about 2 and a half hours. (When charging red light, stop charging green light)






Output coupling DC blocking capacitor using Ina SILMICII 220uF ELNA silk fiber purple palm brown audio electrolytic capacitors, the strength of the extraordinary enough to be among the ranks of the world's advanced audio capacitors. Using the OFC oxygen-free copper feet, very low distortion (third harmonic distortion-120dB), very small tangential loss, natural silk fiber media, high-quality sound, play silk soft and natural, enhanced resistance to acoustic oscillation design, Increase the sense of low-frequency thick, reduce the high-pass part of the peak value of the Peak and the middle part of the rough sound quality.


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## Ivan TT (Aug 21, 2017)

More eye-candy:


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## Ivan TT (Aug 21, 2017)

Ivan TT said:


> Overall F1 is a mixed bag for me right now...
> 
> I had to employ a 100ohm attenuator as when used with Z2's LO F1 is obscenely loud on the balanced out, so much so that only about 10% of potentiometer travel is usable and it's a safety hazard. It distorts when using se (3.5mm) out. Too much bass (at least with muses02), but it depends on the recording. This will require tweaking/fixing, I'm already thinking about adapting buffers for se out (drv134pa allows for this by grounding L- and R- I believe, but the trick is to not to lose balanced out).
> 
> But when you find a sweet spot on the balanced out... it's absolutely wonderful, full-bodied, layers and layers of sound, bets sounstage ever,  details I never heard in the recordings I know by my heart. It works well on some tracks Z2 struggled with and anything hi-rez (especially DSD) is totally immersive.





dmz555 said:


> Thanks for the update Ivan TT.
> Just for claricifaction.
> Out of the box does the 3.5mm SE PO sounds weird? Or it only started soundingweird when you installed muses02 opamp?
> Have you encountered any weird problems in its 2.5mm balanced PO when using stock opamp?
> ...


After a bit of research and experiments I think it's been made to drive high-impedance earphones, hence distortion from the 3.5mm SE output and extremely loud 2.5mm balanced output when using low-impedance IEMs.
I found a pair of 600Ohm AKG 240 (not even mkII verision!) and indeed, no distrtion from 3.5mm SE output.
So, essentially F1 is permanently set to High gain to drive high-impedance earphones, so when using LO from Z1's output and low-impedance earphones you either get distortion and low headroom on 3.5mm SE output, or extremely high output on 2.5mm balanced one.
Possible solutions are: use attenuator (either on the input, or on the output, but I'm not aware of 2.5mm balanced attenuators even existing), or try to feed F1 from PO output:





My solution (warning! this is now obsolete and better solution is in post #9) was to reduce the gain by employing two 5kOhm resistors in parallel with the stock one in opamps feedback loop, over contacts 1-2 and 6-7 of opamp's socket:










I'm still experimenting with the resistors values and other ways to solve this issue (i.e. adding resistor before input cap), but distortion is all but gone and 2.5mm se output volume control range is about 80% before it becomes too loud, eventually I plan to solder resistors in when I find a value that works 100% for me.


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## Ivan TT

After reducing op-amps gain as described above, I finally could evaluate F1's sound and I like it very, very much, even after returning to stock BB opamp and using se 3.5mm output, in my view definitely an upgrade to using Z2's PO out. I will post more impressions later on as I'm still going trough my reference tracks, but so far I like what I hear a lot.


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## benedium (Aug 21, 2017)

Is this headphone amplifier good for full size headphone like Superlux HD681 (32ohm impedance)? Or still have to do modìfications? Also wondering if i should buy this or the Fiio a1.


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## Ivan TT

benedium said:


> Is this headphone amplifier good for full size headphone like Superlux HD681 (32ohm impedance)? Or still have to do modìfications? Also wondering if i should buy this or the Fiio a1.


I have some 32-55-64ohm headphones at work, will check in couple of hours, standby.


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## Ynot1 (Aug 21, 2017)

Any chance there is a high impedance balanced earphone cable, using resistors that are sonically pleasing?
I think the VE Zen balance might be a good match for this amp. Actually VE has a new flagship coming up. And maybe some headphones with high impedance, but I can't think of any except hd600 and beyers. And those may have aftermarket balance cables.


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## dmz555

Thanks alot Ivan TT.
Im really interested in walnut f1's 2.5mm balanced PO and pair it with zishan z2's LO. 
The big question is.
Out of the box without performing  any modifications, can f1 sweetly drive a 32 ohm 2.5 balanced earbuds?


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## Ivan TT (Aug 22, 2017)

Distortion solution #1 did not work as nicely as I expected, so here comes solution #2:
260k resistors (actually 130kx2) in series with input capacitors.






This brought output level on 3.5mm se out to exactly same level as Z2, obviously balanced will be 6dB louder.

I tried a range of values for input resistors, from 100kOhm to 330kOhm, 260kOhm gave a touch of distortion at the very end of the volume potentiometer's travel, unlike lower values where distortion would kick in earlier on).

Replacement capacitors are 110uF (not 220uF as in stock and I don't think 220uF Muse BPs would fit) as CH9T is too good at ultra LF reproduction, which was bothering me a bit.

I also had to move battery back as Nichicons are wider.

Input caps are Elna Silmic II 10uF 35v


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## Ivan TT

dmz555 said:


> Out of the box without performing any modifications, can f1 sweetly drive a 32 ohm 2.5 balanced earbuds?


Yes, but only about first 10-15% of volume pot travel would be usable, as anything above that is obscenely loud (albeit distortion-free unlike on 3.5mm out).

Also I believe it's a safety hazard as it's way to easy to accidentally turn the volume dial too far with about 90% of it's travel are in painfully loud territory.


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## Ivan TT

Now, how do I take the output from buffers and send it to 3.5mm, preferably with automatic switching between the two?





Has anyone seen 8 pole 4 pin 2.5mm sockets anywhere?


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## dmz555

Thank you so much Ivan for that quick reply! This f1 really gets your tech side in action. I will be looking forward on your project to make this f1 work flawlessly.


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## MuZo2

So there is design fault?


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## Ivan TT

MuZo2 said:


> So there is design fault?


I'm not a designer, not even related.
My understanding is that it's been designed to be used with high-impedance transducers, but not advertised as such. Why designers did not include gain switch is beyond me.

By the way, after putting in LME49720NA I'm in the Audiophile heaven, I have Muses02 in Z2 and muses absolutely pales in comparison, not even close.


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## MuZo2

Ivan TT said:


> By the way, after putting in LME49720NA I'm in the Audiophile heaven


Is this with your mod?


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## Ivan TT

MuZo2 said:


> Is this with your mod?


Yes, using se 3.5mm out.


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## RyanM (Aug 22, 2017)

I've just received the F1 today and I want to offer up a few tidbits of info. Firstly the clarity and power is absolutely remarkable. Not having any previous Zishan or Walnut, i have no baseline for this. I'm floored. Secondly, the volume knob is sensitive, but maybe not as sensitive as some have reported. I have noticed that running from my iPhone SE to the "Power Out", rather than "Line In" effectively bypasses the volume knob altogether. With this setup, I can use the volume through my iPhone to control the volume of the F1. It provides far more than enough power to still drive my Zen 2 balanced, while I also dont have to worry about blowing out my earphones or eardrums. I dont know if this is effectively also a "low" gain setting, but it seems to be working that way. Another thing is that I'm able to use a 3.5mm to 2.5mm adapter to run absolutely any standard earphone via the balanced port. The adapter I'm using was included with my 3.5mm balanced VE Zen 2. Anyways, this thing is an absolute marvel. I don't know what the balance out is doing behind the scenes or what percentage of it may or may not be gimmicky, but the results vs. price ratio is truly sensational.


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## Ivan TT (Aug 22, 2017)

RyanM said:


> running from my iPhone SE to the "Power Out", rather than "Line In" effectively bypasses the volume knob altogether


What a great idea, I never even considered it!

This bypasses F1's opamp altogether, tapping into the balanced output stage (and the boost it delivers) directly.

I modded mine to feed balanced buffers into 3.5mm se out (in addition to 2.5mm balanced), only two headphone outs are soooooo last century!


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## Ynot1 (Aug 23, 2017)

RyanM said:


> I've just received the F1 today and I want to offer up a few tidbits of info. Firstly the clarity and power is absolutely remarkable. Not having any previous Zishan or Walnut, i have no baseline for this. I'm floored. Secondly, the volume knob is sensitive, but maybe not as sensitive as some have reported. I have noticed that running from my iPhone SE to the "Power Out", rather than "Line In" effectively bypasses the volume knob altogether. With this setup, I can use the volume through my iPhone to control the volume of the F1. It provides far more than enough power to still drive my Zen 2 balanced, while I also dont have to worry about blowing out my earphones or eardrums. I dont know if this is effectively also a "low" gain setting, but it seems to be working that way. Another thing is that I'm able to use a 3.5mm to 2.5mm adapter to run absolutely any standard earphone via the balanced port. The adapter I'm using was included with my 3.5mm balanced VE Zen 2. Anyways, this thing is an absolute marvel. I don't know what the balance out is doing behind the scenes or what percentage of it may or may not be gimmicky, but the results vs. price ratio is truly sensational.



What you are doing is tying negative left with negative right when they could be at different voltage reference levels. It doesn't seem like a good thing to do. I wonder if this is similar to a scenario when you bi-amp using two amps to drive the same load. I remember in circuit theory a little bit and I think there could be race condition. But if you say it works without problems then interesting. 

Current flows from pos to neg terminal, and electrons flow opposite direction. Based on this one channel could be supplying the electrons to both channels and introduce crosstalk in theory.


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## Ivan TT (Aug 24, 2017)

Ivan TT said:


> I modded mine to feed balanced buffers into 3.5mm se out (in addition to 2.5mm balanced), only two headphone outs are soooooo last century!


So, with this mod and Z2 the following configurations are available, they all give different sonic characteristics:

Z2 Line Out -> F1 op-amp -> 3.5mm out
Z2 Line Out -> F1 op-amp -> buffer amp -> 3.5mm (or 2.5mm balanced) out
Z2 opamp (PO) -> F1 buffer amp -> 3.5mm(or 2.5mm balanced) out
Z2 opamp (PO) -> F1 op-amp -> 3.5mm out
Z2 opamp (PO) -> F1 op-amp -> buffer amp -> 3.5mm(or 2.5mm balanced) out,
and also a VERY interesting one: Z2 Line Out ->  buffer amp -> 3.5mm (or 2.5mm balanced) out, no opamps, no volume control.

I noticed that there's a bit of noise coming from buffer output, so I reduced F1's opamp gain by adding 12kOhm resistors in parallel in feedback loop, this matched the gain of Z2's amp and gave reasonable level when bypassing opamps using last option above. 

With this mod I can use buffered output can to drive headphones using extra 3.5mm socket (F1 handles up to 64Ohm easily), this is not possible with 2.5mm balanced output unless headphones are modified for balanced operation.

Effectively I can choose opamp to match the music I'm listening to on the go (currently Burson v5i in Z2, LME49860NA in F1), add extra power if needed by tapping into buffers, or listen to DAC's output (LO) + gain provided by buffers.

It also gets a bit crowded inside of my F1


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## silverfishla

Ivan TT said:


> So, with this mod and Z2 the following configurations are available, they all give different sonic characteristics:
> 
> Z2 Line Out -> F1 op-amp -> 3.5mm out
> Z2 Line Out -> F1 op-amp -> buffer amp -> 3.5mm (or 2.5mm balanced) out
> ...


hey, what value are those green nichicons?


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## Ivan TT

silverfishla said:


> hey, what value are those green nichicons?


110uf (as opposed to 220uf in stock)


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## RyanM

Ynot1 said:


> What you are doing is tying negative left with negative right when they could be at different voltage reference levels. It doesn't seem like a good thing to do. I wonder if this is similar to a scenario when you bi-amp using two amps to drive the same load. I remember in circuit theory a little bit and I think there could be race condition. But if you say it works without problems then interesting.
> 
> Current flows from pos to neg terminal, and electrons flow opposite direction. Based on this one channel could be supplying the electrons to both channels and introduce crosstalk in theory.



Well, I would hope that there is no negative effects to the F1, however, the alternative is blowing my eardrums out of my head on accident, so I think I'll take that risk. The sound quality is identical to my ears so no worries there.


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## activatorfly

I'd like to order the F1, please can anyone recommend a balanced silver cable for Rose Masya (2-Pin 0.75mm) earbuds?


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## RyanM

activatorfly said:


> I'd like to order the F1, please can anyone recommend a balanced silver cable for Rose Masya (2-Pin 0.75mm) earbuds?



The Venture Electronics SPC cables are fantastic for the price: 

http://s.aliexpress.com/M7JJrAV7


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## activatorfly

Thanks!


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## activatorfly (Aug 29, 2017)

Is the (balanced output) configuration using: Z2/LO & "power out" on the F1 working ok?


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## DBaldock9 (Sep 3, 2017)

Ivan TT said:


> I'm not a designer, not even related.
> My understanding is that it's been designed to be used with high-impedance transducers, but not advertised as such. Why designers did not include gain switch is beyond me.
> 
> By the way, after putting in LME49720NA I'm in the Audiophile heaven, I have Muses02 in Z2 and muses absolutely pales in comparison, not even close.



Did you try installing the LME49720NA, before doing any of the capacitor & resistor mods?  How did it sound?

The reason I ask, is that I received my F1 yesterday - and the first thing I did, after charging it, was to connect it up to the Line Out of my Fiio Taishan D3 DAC (w/TOSLINK input from PC), and verify that the Balanced output would work to drive some **** PT15 earphones.  It did, and sounded very good.  I've also tested the Balanced output with low-ish impedance (16Ω - 32Ω) earphones, and higher impedance (115Ω - 650Ω) earbuds - all with good results.

The second thing I did, was to pop the LME49720HA (TO-99 round metal case) out of my Z1, and swap it for the OPA2134PA in the F1 (which I noticed has terrible DIP sockets - I'll be replacing them).  When I turned it On, I was hearing a good deal of noise.  I thought it might be due to the cover not being on the Amp, but it won't fit, since the TO-99 can is too tall.  So I popped out the LME49720HA, and installed a LME49720NA, and replaced the cover - but the noise was still there.

Next, I tried a PHILIPS NE5532N (Vintage - mid-90s), and it sounded good, but also had some noise, which is audible between tracks, and during quieter parts of the music.

The last thing I did, was to install an OPA2604AP, and it sounds good, without any audible noise.  Which means the two Burr Brown / TI opamps I've got, will both work well in the F1, but not the other brands / models.

So that comes back to my original question - is there something you did, which allows your LME49720NA to work in the F1, without audible noise?

Thanks,
David Baldock


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## Ivan TT

DBaldock9 said:


> So that comes back to my original question - is there something you did, which allows your LME49720NA to work in the F1, without audible noise?



Yes, I had a problem with background noise too, fixed it (and distortion on PO out, to a degree) by reducing opamp's gain, adding 12kOhm resistors between terminals 1-2 and 6-7.


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## activatorfly

Is the power rating of these 2 resistors critical??  I just bought 0.6W (12K Ohm) & was offered 2W as an alternative ...which seemed huge in comparison!


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## Ivan TT

The ones I've got are 1/2W metal film (the latter IS critical).


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## silverfishla

Ivan TT said:


> The ones I've got are 1/2W metal film (the latter IS critical).


Was the buzz introduced during all th capacitor changes or was it always there?  Does it have anything to do with the op-amps that are being used or is it inherent in the F1 from the get go?


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## Ivan TT

silverfishla said:


> Was the buzz introduced during all th capacitor changes or was it always there?


Was always there, but its not a buzz, but white noise.
The reason is that F1's amp has gain of 11 (as far as I understand) as in "classic" CMOY design, and it wrecks havoc with gain staging when using with Z2's LO, bringing noise floor way too up and reducing the range of the volume pot.
So reducing opamp's gain by adding resistors in parallel brings noise floor down, improves volume range and while there is still a bit of distortion at the top of volume pot travel when using "Power out", there's no noise or distortion when utilising buffered out and volume control range is more effective (and safe).
After this mod my F1 has totally "black" background.


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## Ivan TT

Burson or muses predicament is easily solved by F1: why not have both?


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## activatorfly

Ivan TT said:


> The ones I've got are 1/2W metal film (the latter IS critical).


Cool thanks....mine are 0.6W metal film.


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## silverfishla

Ivan TT said:


> Was always there, but its not a buzz, but white noise.
> The reason is that F1's amp has gain of 11 (as far as I understand) as in "classic" CMOY design, and it wrecks havoc with gain staging when using with Z2's LO, bringing noise floor way too up and reducing the range of the volume pot.
> So reducing opamp's gain by adding resistors in parallel brings noise floor down, improves volume range and while there is still a bit of distortion at the top of volume pot travel when using "Power out", there's no noise or distortion when utilising buffered out and volume control range is more effective (and safe).
> After this mod my F1 has totally "black" background.


@Ivan TT  Hey, I was wondering...where do you hear the "white noise"?  Can you hear it with the volume pot turned all the way down on the F1?  I just got the Walnut amp this afternoon, and I can't really hear it.  I'm using a Zishan Z2 (with Muses02 in it, if that matters to you).  It sounds pretty clean, even with the F1 volume turned all the way up (you know, sending all the power to the caps and all).  I have a volume "thingy" in between the line out of the Zishan and the Walnut so that I can toggle the LO and turn up the F1.  Here's a pic, so that I can prove I'm not BS'ing! hahaha!   It's a volume thingy that actually came with a pair of Shure 500 series earphones.  I thought it would work here, and it does without changing the SQ (as far as I can tell by AB'ing with and without it).


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## Ivan TT (Sep 6, 2017)

Yup, I used a similar one that came with UE TF10, 100Om attenuator.
Great minds think the same 
To be honest I don't remember the configuration where that white noise was present, but I remember it disappearing after I reduced gain by soldering in those 12k resistors over opamp's terminals, and I think it was present when plugging into F1 power out (the middle one), but not line in (or was it other way around?). Try plugging your Z2 PO into F1's power out?
I have muses02 in my F1, by the way


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## silverfishla

Ivan TT said:


> Yup, I used a similar one that came with UE TF10, 100Om attenuator.
> Great minds think the same
> To be honest I don't remember the configuration where that white noise was present, but I remember it disappearing after I reduced gain by soldering in those 12k resistors over opamp's terminals, and I think it was present when plugging into F1 power out (the middle one), but not line in (or was it other way around?). Try plugging your Z2 PO into F1's power out?
> I have muses02 in my F1, by the way


Interesting connection theories there! Hahaha!  I think it's neat that you can plug in 3 headphones at the same time and have them all running at the same time from all the open jacks.


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## DBaldock9

I was really hoping the F1 would last longer than a week.

Now, it makes a bit of a distorted sound - and goes quiet after a few seconds.

Noticed that the Charging LED was going On & Off, with any movement of the USB cable... 

****  Intermission - While I check the Solder  ****

Found several of the through-hole solder joints that weren't done well including the ones for the USB connector.  Also touched-up quite a few of the surface mount solder joints.

The F1 Amp is working again now...


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## TheoS53

Just received my F1 (ordered from Penon). I was particularly interested in getting a bit more involved in the DIY side, so the F1 seemed like a decent place to start.

However, when I opened the F1 up, I noticed that it does NOT have the large ELNA capacitors as advertised. Also, oddly enough it seems to have a 2000mah battery instead of a 1500. Anyone know why mine would be different?


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## Ivan TT

Better battery is nice and F1 would definitely benefit from it. What is the code on it, cannot quite see on the photo?
As for the caps, it's not uncommon for those DIY devices to use substitutes due to (I assume) their supply chain. Aren't you replacing them anyway though?


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## TheoS53 (Sep 17, 2017)

Ivan TT said:


> Better battery is nice and F1 would definitely benefit from it. What is the code on it, cannot quite see on the photo?
> As for the caps, it's not uncommon for those DIY devices to use substitutes due to (I assume) their supply chain. Aren't you replacing them anyway though?



Yeah, I do want to replace and play around. But part of the reason I got the F1 was because I said it had the Elna caps. I've seen them get good ratings for tube amps, so I was curious to try them out.

I had a look on mouser but couldn't find the same ones that were originally used (220uf 10V)


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## Robert Turnbull

Quick question, does the mod on post #9 reduce the gain only on the 3.5 mm SE, or for both the 2.5 mm and the 3.5 mm?

I quite like how powerful the 2.5mm is already... But i would like to cut the gain of the 3.5mm....


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## activatorfly

Robert Turnbull said:


> Quick question, does the mod on post #9 reduce the gain only on the 3.5 mm SE, or for both the 2.5 mm and the 3.5 mm?
> 
> I quite like how powerful the 2.5mm is already... But i would like to cut the gain of the 3.5mm....


I agree....the balanced output is fine - doesn't need clipping....


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## Ivan TT

Robert Turnbull said:


> I quite like how powerful the 2.5mm is already... But i would like to cut the gain of the 3.5mm....


Yes, it reduces input gain of signals feeding thru Line In.


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## Sam Wayne (Sep 23, 2017)

Hello,
I am looking to buy F1 or V2s . Does F1 has shielding so that interference from RFs are minimised ? Because I am going to use with mainly with my phone.


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## DBaldock9

Sam Wayne said:


> Hello,
> I am looking to buy F1 or V2s . Does F1 has shielding so that interference from RFs are minimised ? Because I am going to use with mainly with my phone.



No.  It seems to be fairly susceptible to EMI / RFI - especially if the USB cable is connected (to charge the battery, while the amp is in use).

It might have better isolation, if you made a determined effort to assure that the Top, Bottom, Front, & Rear panels are all connected to the circuit board GND.  I haven't done this yet, but it is one of my planned F1 mods (along with lowering the gain, upgrading the IC sockets, upgrading the Op-amp, and upgrading the Capacitors).


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## Sam Wayne

DBaldock9 said:


> No.  It seems to be fairly susceptible to EMI / RFI - especially if the USB cable is connected (to charge the battery, while the amp is in use).
> 
> It might have better isolation, if you made a determined effort to assure that the Top, Bottom, Front, & Rear panels are all connected to the circuit board GND.  I haven't done this yet, but it is one of my planned F1 mods (along with lowering the gain, upgrading the IC sockets, upgrading the Op-amp, and upgrading the Capacitors).


Thank You very much. Then i  have to buy FIIO Q1 as it has good shielding. Topping also advertises its NX2s model to be used as DAc but I am not sure of the shielding. No cheap amp with shield then.


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## DBaldock9 (Sep 24, 2017)

Sam Wayne said:


> Thank You very much. Then i  have to buy FIIO Q1 as it has good shielding. Topping also advertises its NX2s model to be used as DAc but I am not sure of the shielding. No cheap amp with shield then.



I was speaking specifically of the F1.

*EDIT: Change *(_I haven't used the V2s much, as an Amp.  My V2s_) *to* I don't have a v2S, but I did use my v2 a couple of times as an Amp, and don't remember it being too noisy (wasn't using it with my phone).  My v2 is currently disassembled (being modified), so I can't tell you how susceptible it is to EMI / RFI.


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## TheoS53

Sam Wayne said:


> Thank You very much. Then i  have to buy FIIO Q1 as it has good shielding. Topping also advertises its NX2s model to be used as DAc but I am not sure of the shielding. No cheap amp with shield then.



Fiio A3?


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## Sam Wayne

TheoS53 said:


> Fiio A3?


Actually, here in India Fiio A3 costs around 70 USD and Fiio Q1 costs 79 USD, so was thinking about Q1. But am not sure which will give better quality with my phone. I am concerned about the hissing noise many users complain about when amplifying from a phone.


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## Sam Wayne

DBaldock9 said:


> I was speaking specifically of the F1.
> 
> *EDIT: Change *(_I haven't used the V2s much, as an Amp.  My V2s_) *to* I don't have a v2S, but I did use my v2 a couple of times as an Amp, and don't remember it being too noisy (wasn't using it with my phone).  My v2 is currently disassembled (being modified), so I can't tell you how susceptible it is to EMI / RFI.


Thank You. I am actually looking for a cheap but powerful amp. How is Zishan Z2? Do you have any experience with that?


----------



## TheoS53

Sam Wayne said:


> Actually, here in India Fiio A3 costs around 70 USD and Fiio Q1 costs 79 USD, so was thinking about Q1. But am not sure which will give better quality with my phone. I am concerned about the hissing noise many users complain about when amplifying from a phone.



Ok, I see you haven't made many posts, so I'm going to assume that you're fairly new to this audio game. Double amping isn't ideal, which is what you'd be doing if you connected any amp to your phone's headphone port (unless the phone has a lineout function). As such, your best bet with a mobile device is always to rather use a DAC/AMP combo like the Q1. But take the time to Google and make sure that your phone is capable of outputting audio to an external DAC. On Android this is called OTG *HOST* functionality. And then you'll need a compatible app which would be able to communicate with the external device. Hiby Music is a great app on Android, and it's totally free


----------



## Sam Wayne (Sep 24, 2017)

TheoS53 said:


> Ok, I see you haven't made many posts, so I'm going to assume that you're fairly new to this audio game. Double amping isn't ideal, which is what you'd be doing if you connected any amp to your phone's headphone port (unless the phone has a lineout function). As such, your best bet with a mobile device is always to rather use a DAC/AMP combo like the Q1. But take the time to Google and make sure that your phone is capable of outputting audio to an external DAC. On Android this is called OTG *HOST* functionality. And then you'll need a compatible app which would be able to communicate with the external device. Hiby Music is a great app on Android, and it's totally free


Thank you for your quick reply. I have not many posts but I have read through the Headfi forums and websites like Headfonia, Headfonics, WhatHiFi and many such sites. I made the account just recently to talk about Walnut V2s and F1. I may not have any expensive audio gear at present because I am a college student but I intend to experience quality audio in future. I thought of buying Audioquest Dragonfly Black but it is pretty expensive for me. I have OP3T and Hibymusic and Onkyo HF player installed. But I am not sure if OP3T will support Q1. That's why I am looking for DAC/AMPs such as Topping NX2s. Then amps such as Walnut F1 because they can act as stopgap devices fort he time being.
P.S. Just ordered Monk+ though. Waiting for it now.


----------



## DBaldock9

Sam Wayne said:


> Thank You. I am actually looking for a cheap but powerful amp. How is Zishan Z2? Do you have any experience with that?



It's on my wishlist, since it's reported to sound better than the Z1 & v2.

*BUT* - there are reports that the Zishan Z2 does not function as an Amp, if you plug a _Line In_ cable into the _Line Out_ port, like you can on the Walnut v2 models.
So, to use it as an Amp, you have to be connected via USB, and using it as a DAC / Amp.


----------



## Sam Wayne

DBaldock9 said:


> It's on my wishlist, since it's reported to sound better than the Z1 & v2.
> 
> *BUT* - there are reports that the Zishan Z2 does not function as an Amp, if you plug a _Line In_ cable into the _Line Out_ port, like you can on the Walnut v2 models.
> So, to use it as an Amp, you have to be connected via USB, and using it as a DAC / Amp.


But it is also likely to be suffering from the same EMI/RFI issue.


----------



## DBaldock9

There are two electrolytic capacitors, standing upright - very near the Op-Amp socket.
I'm going to replace them with some that are moved a bit further away, and laying down.

Then, I'm going to install a modified BrownDog (P/N 111001) "DIP-8 -to- 2x Single TO-99 adapter" in-place of the Op-Amp socket.
http://cimarrontechnology.com/single-to-dualop-ampadapter-to99.aspx
The mods to the adapter will consist of:
1.) Replacing the standard solder pins, with DIP socket pins.
2.) Installing socket pins for the TO-99 devices.
This will allow me to use dual LME49710HA Op-Amps, or remove them, and plug in a DIP-8 style Op-Amp (like a MUSES02).
Soldering the multi-adapter to the board will be lower than plugging an TO-99 Op-Amp into the stock DIP-8 socket (i.e.- it should fit under the battery, and allow the case to close).


----------



## Yobster69

Hi all. I am looking to get the F1 and will be feeding it via an iPhone and the LO from my Oppo HA-2 amp, so I am able to change the level of volume output from the DAC as well as the F1, so I have a good control of its overall output. 
My question is this, are the 2 outputs of the F1 different in sound signature, so that I am able to notice a difference between them when listening single ended and balanced on the same phones? And are both decent enough that it would give me an option of 'flavours' if you will? 
Thanks in advance


----------



## activatorfly (Sep 29, 2017)

Yobster69 said:


> Hi all. I am looking to get the F1 and will be feeding it via an iPhone and the LO from my Oppo HA-2 amp, so I am able to change the level of volume output from the DAC as well as the F1, so I have a good control of its overall output.
> My question is this, are the 2 outputs of the F1 different in sound signature, so that I am able to notice a difference between them when listening single ended and balanced on the same phones? And are both decent enough that it would give me an option of 'flavours' if you will?
> Thanks in advance


Balanced is much better than SE...which has a strangely muted sound signature. I only use it now for balanced output tbh which has much more sparkle! - you could try rolling the op-amp or replacing output gain capacitors, however it's hard to recommend the SE option....


----------



## Yobster69

activatorfly said:


> Balanced is much better than SE...which has a strangely muted sound signature. I only use it now for balanced output tbh which has much more sparkle! - you could try rolling the op-amp or replacing output gain capacitors, however it's hard to recommend the SE option....


Thank you, It's not a major surprise to be honest, as I was looking to use this mainly balanced anyway. I know it's not true balanced but it's an intro of sorts, and you never know, the SE might synergise with something I own. It'll be fun trying. And the option to modify is also appealing.


----------



## activatorfly

Yobster69 said:


> Thank you, It's not a major surprise to be honest, as I was looking to use this mainly balanced anyway. I know it's not true balanced but it's an intro of sorts, and you never know, the SE might synergise with something I own. It'll be fun trying. And the option to modify is also appealing.



I hope they address the poor SE issue with the release of V3 - which extends modification/sound signature tuning via three op-amps.
In my opinion, maybe V4 should include a balanced input & output - which would maintain a balanced synergy, rather than compromising the player with substandard SE output...
I guess we'll find out soon if the upgraded SE stage has improved?


----------



## sfogar (Oct 10, 2017)

Hi, is the F1 suitable for IEM like KZ zs5 (i.e. multi dd+ba) ?
Currently I own a Zishan Z1 and the high output impedance is not suitable for the zs5.


----------



## RyanM

sfogar said:


> Hi, is the F1 suitable for IEM like KZ zs5 (i.e. multi dd+ba) ?
> Currently I own a Zishan Z1 and the high output impedance is not suitable for the zs5.



The answer to this is no. In the same price range (check EBay) I’d look at the Topping NX1s - it’s a fantastic little budget amp with high/low gain and a bass boost. Awesome stuff.


----------



## Yobster69

Hi, has anybody measured the output impedance of both sockets of the F1?


----------



## Ivan TT

Changed gain-reducing resistors to smd (probably could get 0805 size instead):






Also upgraded opamp socket:





I recommend adding more solder around micro-USB socket's legs to secure it more firmly, as it easily gets loose/torn off over time, this happened on my F1, Z1 and Z2.


----------



## Wiljen

@Ivan TT any chance we could get of Build list of parts and a recommendation of where to order them?  I think I am going to do at least the cap upgrades and the resistor mod and have been debating the muses or AD8610 swap.


----------



## Wiljen (Nov 3, 2017)

Ivan TT said:


> Yes, I had a problem with background noise too, fixed it (and distortion on PO out, to a degree) by reducing opamp's gain, adding 12kOhm resistors between terminals 1-2 and 6-7.



I am reading those as Red, black, Orange, Gold which makes the resistor a 20K rather than 12 unless I am missing something.  Also did you still have the 2 130k resistors in series with the input caps or is this instead of those?  I noticed in post 20 you don't show the resistor mod on the input caps so am trying do determine if this is one or the other or both that are needed to reduce gain.


----------



## Superluc

Ivan TT said:


> Yup, I used a similar one that came with UE TF10, 100Om attenuator.


How much is the output impedance of the Walnut F1 ?

I have an impedance adapter of 75 ohm and a KZ ZS6 on the way, thinking about using the adapter for tune down the highs, as a graph from @hakuzen show that on the FR with this combo, on a near 1 ohm output source.

Anyway, my through was to buy a Zishan Z2, using directly it if it's higher impedance output work good on balancing the ZS6, or coupling it with my Topping NX2 on the LO, for my other IEMs, and eventually with the combo adapter-ZS6. 

But it said that this F1 AMP is warm, almost tubey, and i may be interested on it, especially for "educate" brighter headphone. 
Putting an adapter of 75 ohm between the Z2 LO and the F1, the F1's power may be that strong for work good with low impedance headphone ? The distortion you have talked about, on stock condition, it's more problematic to handle because of impedance output or too strong gain ?


----------



## Ivan TT (Nov 7, 2017)

Quick recap of mods and parts needed:

1. Input capacitors: (next to opamp socket), I upgraded to 2x 10uF 16V Nichicon BP, arrow, mouser and digikey code UES1C100MDM

2. Output capacitors: 100uF 16V Nichicon BP, code UES1C101MPM

3. Opamp gain reduction (reduces noise and distortion at max level, tapers volume pot): 11kOhm resistors across opamp terminals 1-2 and 6-7, I suggest 0603 SMD, for example CRCW060311K0FKTA

4. Power supply capacitors: 4 x 470uF 16V, for example UHD1C471MPD should work and it is smaller than the one I used.

5. Single ended buffered output mod requires SHORT 3.5mm panel mounted socket (like this one: https://goo.gl/q25TL9 ) and a miniature 6 pin DPDT switch ( like this one: https://goo.gl/LdWSmZ ) They will require a bit of filing to make them fit.

Cables should be wired as per image below (central pins of the switch should be connected with a jumper cable and to the ground, connect 3.5mm socket's ground to them as well, *5* on the image below), when switch is engaged L and R negative outs (*2* and *3*) are grounded, as per SE buffer operation requirements:





Hope it helps.

PS: wire #1 at 2.5mm socket is tricky to solder in as it is way to easy to jump ground sleeve wrapping around the front of the socket from #3 with excessive solder. Insure that there is no solder (and no electrical contact) between solder joint #2 and the sleeve right above it.

F1 + Nichicon BP audio caps:


----------



## Ivan TT

Wiljen said:


> I am reading those as Red, black, Orange, Gold which makes the resistor a 20K rather than 12 unless I am missing something.


I'm not that well versed in electronics, to be honest. I can confirm that 11k resistors work well though.


Wiljen said:


> Also did you still have the 2 130k resistors in series with the input caps or is this instead of those? I noticed in post 20 you don't show the resistor mod on the input caps so am trying do determine if this is one or the other or both that are needed to reduce gain.


Not anymore, I only 11k resistors between opamp's terminals to reduce gain now.


----------



## Merlin-PT (Nov 9, 2017)

I don't have the F1 and looking at posted photos (without mods), I have a basic question about how it works.

Considering these blocks of components (a, b and c):
a) 2x DRV134PA
b) 1x OPA2604
c) 4x what looks like some transistors

What is the audio path from 3,5" IN to 3,5" OUT ?
What is the audio path from 3,5" IN to 2,5" balanced OUT ?

TY


----------



## Ivan TT (Nov 9, 2017)

Merlin-PT said:


> What is the audio path from 3,5" IN to 3,5" OUT ?


Volume pot-input caps-opamp-output caps-3.5mm out (pretty much the same as other Walnut series headphone amps)


Merlin-PT said:


> What is the audio path from 3,5" IN to 2,5" balanced OUT ?


The same as above, but with DRV134PA at the end of the signal flow chain.

There's another option, using 3.5mm OUT as INPUT , this bypasses caps, volume control and opamp, but engages DRV134PAs feeding into 2.5mm balanced out.


----------



## DBaldock9

Ivan TT said:


> Volume pot-input caps-opamp-output caps-3.5mm out (pretty much the same as other Walnut series headphone amps)
> 
> The same as above, but with DRV134PA at the end of the signal flow chain.
> 
> There's another option, using 3.5mm OUT as INPUT , this bypasses caps, volume control and opamp, but engages DRV134PAs feeding into 2.5mm balanced out.



Is that final option only valid if you install the switch on the front - to isolate the output of the Internal Op-Amp from the External Input that you're providing at the 3.5mm Output?


----------



## Ivan TT

DBaldock9 said:


> Is that final option only valid if you install the switch on the front - to isolate the output of the Internal Op-Amp from the External Input that you're providing at the 3.5mm Output?


Not at all, it works quite fine in stock, but I feel it introduces some noise from the opamp's circuit, hence the solution to add gain reduction resistors in opamp's feedback loop.


----------



## cqtek

Hello.

I read all the thread and I know that this model without any modification is useful to use with high impedance earphones, I guess that makes reference for the two outputs, normal and balanced.
My first question is what impedance you consider high, above 64 Ohms, 100 Ohms?
The second question is possible to use this impedance adapters with good result connected to sensitive IEMS without any internal modification of F1?

https://es.aliexpress.com/item/DUNU...0-200-ohm-For-Headphone-HiFi/32832583027.html
https://es.aliexpress.com/store/pro...iFi-Player-Earphone/1994049_32810903635.html?

Also, are there some impedance adapaters for balanced connection?

Thank you.


----------



## theoutsider

https://www.facebook.com/photo.php?...&set=gm.1513426468734713&type=3&theater&ifg=1
from a group on fb.

There's a saying that F1's balance out is basically unusable due to the strong hiss, how true is that?


----------



## Ivan TT

cursing said:


> https://www.facebook.com/photo.php?...&set=gm.1513426468734713&type=3&theater&ifg=1
> from a group on fb.
> 
> There's a saying that F1's balance out is basically unusable due to the strong hiss, how true is that?


I remember having issues with hiss, but it's dead silent (aka "black") with opamp gain mod (11k resistors added in parallel in opamp's gain loop).


----------



## hakuzen

cqtek said:


> Hello.
> 
> I read all the thread and I know that this model without any modification is useful to use with high impedance earphones, I guess that makes reference for the two outputs, normal and balanced.
> My first question is what impedance you consider high, above 64 Ohms, 100 Ohms?
> ...


for usual low impedance sensitive BA IEMs, you need quite the opposite; you need source output impedance lower than 1 ohm, to avoid frequency response alterations.
so high output impedance sources, like this, or impedance adapters, are the worst you can do. kz zs6 is an exception, due to their peculiar impedance curve characteristics.


----------



## Dark Helmet

This may have been covered here already, but does anyone know what the output impedance is of the F1?


----------



## n1kk1

Dark Helmet said:


> This may have been covered here already, but does anyone know what the output impedance is of the F1?


 Up to 400 as advertised


----------



## n1kk1

Can the F1 drive monoprice plantar m1060? Thanks!


----------



## kukkurovaca

n1kk1 said:


> Can the F1 drive monoprice plantar m1060? Thanks!



Works very well with T50RPs, FWIW


----------



## Dark Helmet

n1kk1 said:


> Up to 400 as advertised


Thank you for the reply, but what I am asking is not what Ohm load can they drive. I am asking what is the output impedance. Output impedance determines how it interacts with low Ohm earphones.


----------



## Ivan TT

Dark Helmet said:


> Output impedance determines how it interacts with low Ohm earphones.


50Ohm balanced, 100Ohm SE.
However, I don't think it's interacting with low-impedance earphones in a bad way, at least I did not notice any issues/coloration/noise.


----------



## Wiljen

I've done a resistor mod on one F1 and used the earbuddy with another and both work about equally well.  I have an Ifi-match coming that will replace the earbuddy so I have a few more adjustment options.  It should be about perfect for matching the F1 to lower impedance in ears.  I'll post when I know more.


----------



## Wiljen (Mar 12, 2018)

Ifi-match is not a good match with the F1.  I tried it tonight with the Magaosi K5 as they have a deserved reputation for being super sensitive.  While the match did bring the volume down and get rid of the hiss at the low end of the volume dial, it introduced a ton of distortion at anything over 25% on the pot.   I tried using the Cayin N3 on low gain with volume at 40 of 100 as input and still was only able to use roughly 33% of the dial before the distortion became blatent.   My advice on the F1 if you want to use it with headphones below 100 Ohm would be do the resistor mod on the gain legs of the op-amp.  That has been the most consistent fix of the three options.


----------



## bsoplinger

Ivan TT said:


> Distortion solution #1 did not work as nicely as I expected, so here comes solution #2:
> 260k resistors (actually 130kx2) in series with input capacitors.
> 
> 
> ...


Is there any possibility of posting the image elsewhere? All I see is IMG and the icon representing a bad link


----------



## Onik (Jun 28, 2018)

Ivan TT said:


> Balanced Version= With 2.5mm Balanced out Interface and still have 3.5mm interface
> Standard Version= Only have 3.5mm interface
> 
> WARNING! F1 is designed to drive high-impedance earphones, essentially set to what is high-gain mode on other amps. This leads to distortion (when using 3.5mm se out) or extremely high output level (when using 2.5mm balanced output).  Solution is in post #9.
> ...



My F1 feels like faulty its just constant white noise, Can you please send me more picture of the actual mod for reducing gain and noise on the op amp? I just wanna see how you did solder it.

cheers


----------



## DBaldock9

Onik said:


> My F1 feels like faulty its just constant white noise, Can you please send me more picture of the actual mod for reducing gain and noise on the op amp? I just wanna see how you did solder it.
> 
> cheers



For my F1, I just soldered a pair of 20K 1/8W resistors in parallel, between the op-amp socket pins (1 & 2) and (6 & 7) on the back side of the circuit board -


----------



## Onik

DBaldock9 said:


> For my F1, I just soldered a pair of 20K 1/8W resistors in parallel, between the op-amp socket pins (1 & 2) and (6 & 7) on the back side of the circuit board -



Cool, did it help to reduce the gain and lower the noise?

I just received 2.5mm adapter still noise and the sound stage is really really low, maybe some caps blown up.

btw can I use any 20k registors?


----------



## DBaldock9

Onik said:


> Cool, did it help to reduce the gain and lower the noise?
> 
> I just received 2.5mm adapter still noise and the sound stage is really really low, maybe some caps blown up.
> 
> btw can I use any 20k registors?



You really need 10K - 11K, so if you've got 1/4W resistors of that value, then use them - otherwise you can place a couple of 1/8W resistors in parallel, like I did.
The RF interference noise was reduced a lot, when I lowered the gain.
What sort of 2.5mm adapter did you get?


----------



## Onik

DBaldock9 said:


> You really need 10K - 11K, so if you've got 1/4W resistors of that value, then use them - otherwise you can place a couple of 1/8W resistors in parallel, like I did.
> The RF interference noise was reduced a lot, when I lowered the gain.
> What sort of 2.5mm adapter did you get?



i got this: https://www.ebay.co.uk/itm/2-5mm-Ma...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649


----------



## Ivan TT

I used 11kOhm in early version soldered as per photo, alternatively use 0805 sized smd resistors.


----------



## Onik

Ivan TT said:


> I used 11kOhm in early version soldered as per photo, alternatively use 0805 sized smd resistors.



cool Im gonna do it let you know.


----------



## DBaldock9

Onik said:


> i got this: https://www.ebay.co.uk/itm/2-5mm-Male-to-3-5mm-Female-Earphone-Headphone-Audio-Jack-Adapter-Converter-Cable/282942531525?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649



Is that a 4-pole 2.5mm TRRS plug, to 4-pole 3.5mm TRRS jack adapter?
If it is shorting any of the 4 signals on the 2.5mm TRRS plug together, it's not an appropriate adapter for the F1 Balanced output.


----------



## Ivan TT

Onik said:


> cool Im gonna do it let you know.


You can source resistors from arrow.com - they even have free delivery + 10% discount currently, I actually bought ERJ-P06F1102V a minute ago to replace resistors I currently have in my F1


----------



## Onik

DBaldock9 said:


> Is that a 4-pole 2.5mm TRRS plug, to 4-pole 3.5mm TRRS jack adapter?
> If it is shorting any of the 4 signals on the 2.5mm TRRS plug together, it's not an appropriate adapter for the F1 Balanced output.



I don't know, all I know is its't just a basic adapter, can you send me a link for the right adapter for F1?


----------



## Onik

Ivan TT said:


> You can source resistors from arrow.com - they even have free delivery + 10% discount currently, I actually bought ERJ-P06F1102V a minute ago to replace resistors I currently have in my F1



I find the big ones are easier to solder, why you really want to replace?


----------



## Ivan TT

Onik said:


> I find the big ones are easier to solder, why you really want to replace?


Cleaner this way, but it's a very subjective reason, I agree.

Re: adaptors, it's impossible to have one as L- and R- should be tied to the ground at the line drivers level.

I solved it by adding extra 3.5mm socket and a switch.


----------



## Onik

Ivan TT said:


> Cleaner this way, but it's a very subjective reason, I agree.
> 
> Re: adaptors, it's impossible to have one as L- and R- should be tied to the ground at the line drivers level.
> 
> I solved it by adding extra 3.5mm socket and a switch.



that gain switch is a must have! I got many *Elna Silmic II(brown), *now Im gonna use them for this amp, btw is the 2 buffers can be swapped with op amps like lme49710ha?


----------



## Ivan TT

Onik said:


> that gain switch is a must have! I got many *Elna Silmic II(brown), *now Im gonna use them for this amp, btw is the 2 buffers can be swapped with op amps like lme49710ha?


It's no a gain switch, it switches between balanced and SE out configurations.
DRV134 are balanced line drivers, so are not swappable for opamps, I don't think there is even a pinout compatible IC out there, but they don't sound too bad.


----------



## DBaldock9

Onik said:


> I don't know, all I know is it's just a basic adapter, can you send me a link for the right adapter for F1?



What are you planning to connect to the output of the F1?
The 2.5mm TRRS Balanced output is being driven by the pair of DRV134 Balanced Line Driver chips.
There's also a 3.5mm TRS Single-ended output, which is driven by the LM4562NA op-amp.

If you have balanced earphones, with a 3.5mm TRRS plug, then you can verify that the adapter you've found is correct - by plugging in you earphones, and then testing the 2.5mm plug with an Ohmmeter.
With the earphones on, measure between the Tip and Ring-1 - and you should hear a click in your right ear, and see the resistance reading of right earpiece.
When you measure between Ring-2 and the Sleeve - you should hear a click in your left ear, and see the resistance reading of the left earpiece.
If that works, then you can use the 2.5mm TRRS plug -to- 3.5mm TRRS jack adapter for your 3.5mm TRRS earphones.
If it doesn't work, then you can order a 2.5mm TRRS plug -to- 3.5mm TRRS jack adapter from VE Clan (for $5 - $20+, depending on parts used) - https://www.veclan.com/engappliance_sel_one?eng_ApplianceVo.eac_id=17


----------



## Onik

Ivan TT said:


> It's no a gain switch, it switches between balanced and SE out configurations.
> DRV134 are balanced line drivers, so are not swappable for opamps, I don't think there is even a pinout compatible IC out there, but they don't sound too bad.



Lol I was sure that it was, ok if not op amp can I swap them with better balanced line drivers to make sound even more cleaner?


----------



## DBaldock9

Ivan TT said:


> It's no a gain switch, it switches between balanced and SE out configurations.
> DRV134 are balanced line drivers, so are not swappable for opamps, I don't think there is even a pinout compatible IC out there, but they don't sound too bad.



I've got all three of the pin-compatible SE to Balanced Line Driver chips -
1.) TI DRV134PA - Single Channel Differential Line Driver (stock in F1) [2x]
2.) AD SSM2142PZ - Single Channel Differential Line Driver [2x, $6.28 ea]
3.) THAT 1646P08-U - Single Channel Differential Line Driver [2x, $4.87 ea]

Both the AD and THAT chips are available from Mouser Electronics.
Currently, the AD SSM2142PZ chips are installed, and I think I like their sound the best.

What I'd really like to do, is redesign the output circuit, to use the THAT 1606Q16-U - since it has a differential Input, as well as the differential output.
The difficulty is that the "Q16" mean that it's a QSOP-16 package, which is a very small surface mount chip.


----------



## Onik

Done


----------



## Onik

now I no longer hear any noise(BLACK), thanks a lot for your help. I really thought that I wasted my £20 LOL. Now I am gonna try different op amps to find the best setup for this little amp.


----------



## Onik

DBaldock9 said:


> Is that a 4-pole 2.5mm TRRS plug, to 4-pole 3.5mm TRRS jack adapter?
> If it is shorting any of the 4 signals on the 2.5mm TRRS plug together, it's not an appropriate adapter for the F1 Balanced output.





DBaldock9 said:


> What are you planning to connect to the output of the F1?
> The 2.5mm TRRS Balanced output is being driven by the pair of DRV134 Balanced Line Driver chips.
> There's also a 3.5mm TRS Single-ended output, which is driven by the LM4562NA op-amp.
> 
> ...



Is the 2.5 balance out only for Blanced iems? cus with the adapter I have don’t seems its working,maybe you are right it’s shorting something.

I’ll need spend another £10 for the right adapter now.


----------



## DBaldock9

Onik said:


> Is the 2.5 balance out only for Blanced iems? cus with the adapter I have don’t seems its working,maybe you are right it’s shorting something.
> 
> I’ll need spend another £10 for the right adapter now.



Yes, the 2.5mm TRRS Balanced output is designed to drive balanced devices, where all four signals (L+, L-, R+, R-) are kept separate.
You only need to get a different 2.5mm to some other jack adapter, if you're actually driving a balanced load.
Use the 3.5mm TRS Single-Ended output for standard 3-wire (L+, R+, GND) headphones / earphones / earbuds.


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## Themilkman46290

Would it be possible to add a toggle switch between resistors? To have high/ low gain?


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## DBaldock9 (Jul 9, 2018)

Themilkman46290 said:


> Would it be possible to add a toggle switch between resistors? To have high/ low gain?



Your best bet, would be to select a resistor for your maximum required gain, and then add a switch that puts another resistor in parallel, to reduce the gain to the desired lower level.
That way, you always have a gain controlling resistor in the circuit, which wouldn't be the case, if you're switching between two separate resistors.


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## Onik

How can I replace my broken 3.5mm port?? Can Someone send a link for replacement port?


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## DBaldock9

Onik said:


> How can I replace my broken 3.5mm port?? Can Someone send a link for replacement port?



This appears to be the correct part - https://www.aliexpress.com/item/10p...ted-6-feet-Double-track-gold/32879818101.html
But, it looks like you'll have to repair at least one of the solder pads - top-right pad in the photo.


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## Onik

DBaldock9 said:


> This appears to be the correct part - https://www.aliexpress.com/item/10p...ted-6-feet-Double-track-gold/32879818101.html
> But, it looks like you'll have to repair at least one of the solder pads - top-right pad in the photo.



Do I really need that pad?

And btw if I use only balanced iems do I still need that port?


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## DBaldock9

Onik said:


> Do I really need that pad?
> 
> And btw if I use only balanced iems do I still need that port?



Just checked, and that pad, along with the one across from it, provides the *GND* signal for the 3.5mm jack. 
If you're not using the unbalanced output, then there's no need to have the 3.5mm earphone jack.


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## IcedFrosty

Hello, 
I've been wondering how does the F1 and V3 converts a single-ended input into a balance out? I need a simple block diagram for both F1 and V3 from the input to the 2.5mm output. Can anyone who understand electricity and audio signal path kindly explain this to me? 

Thank you very much, 
God bless.


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## DBaldock9

IcedFrosty said:


> Hello,
> I've been wondering how does the F1 and V3 converts a single-ended input into a balance out? I need a simple block diagram for both F1 and V3 from the input to the 2.5mm output. Can anyone who understand electricity and audio signal path kindly explain this to me?
> 
> Thank you very much,
> God bless.



Here's a simple diagram of the F1 circuit - 
.


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## Merlin-PT (Oct 2, 2019)

They use DRV134 ?

EDIT:
I see a photo of DRV134 in 1rst post, but no reference to it in the specs.
@IcedFrosty
Take a look at DRV134 datasheet, it does it all.


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## DBaldock9

I found that they used the DRV134, either from what was written on the original sale page, or from the photo on that page.


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## DBaldock9

One thing to consider about the Differential Line Drivers, is that they are really designed to drive 600-Ohm balanced line level signals.


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## ricesteam

Anyone know if this device can operate without the battery?


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## DBaldock9

ricesteam said:


> Anyone know if this device can operate without the battery?



Yes, the F1 will work without the battery connected.
Although, when I've run mine without the battery, I was using a USB Charger that can supply 2.1 - 2.4A of current.
You may end up with audio distortion if you use a low current power supply (like a 0.5A PC USB port).


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## DBaldock9

For those who have a Walnut F2, on my modified model (op-amps replaced with MUSES-8920E, Differential Line Drivers replaced with AD SSM-2142SZ), I was able to play WAV files of my CD .flac rips, for a little over 6 hours on a battery charge today, using the Balanced output, driving various IEMs.


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## prionsarebad

DBaldock9 said:


> For those who have a Walnut F2, on my modified model (op-amps replaced with MUSES-8920E, Differential Line Drivers replaced with AD SSM-2142SZ), I was able to play WAV files of my CD .flac rips, for a little over 6 hours on a battery charge today, using the Balanced output, driving various IEMs.


I am thinking of getting the F2.

Will there be any issue, as far as you know, using it as a DAC/amp on my phone and UAPP?

Also, in your opinion, what are the best, cheap op amps to roll with on the F2? I prefer a rich, analogue sound, v-shaped.... Old school 

Thanks!


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## DBaldock9

prionsarebad said:


> I am thinking of getting the F2.
> 
> Will there be any issue, as far as you know, using it as a DAC/amp on my phone and UAPP?
> 
> ...



I haven't tried to use the F2 with my phone, since my LG V30 has a _much better_ DAC chip in it.
As a USB DAC, the F2 only supports playing 16-Bit / 44.1-KHz or 48-KHz WAV or MP3 files.

While it's been discontinued, there appears to be one LME-49720-HA - Dual Op-Amp (TO-99 round metal case) still available from the USA on eBay -
https://www.ebay.com/itm/LME49720HA...ise-OpAmp-Metal-case-LME49720-HA/174286005296
If not, the LME-49720-NA - Dual Op-Amp (DIP-8) version is more readily available.
Another Op-Amp with good Bass response is the OPA-1622 - Dual Op-Amp (VSON-10) on DIP-8 header.


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## prionsarebad

DBaldock9 said:


> I haven't tried to use the F2 with my phone, since my LG V30 has a _much better_ DAC chip in it.
> As a USB DAC, the F2 only supports playing 16-Bit / 44.1-KHz or 48-KHz WAV or MP3 files.
> 
> While it's been discontinued, there appears to be one LME-49720-HA - Dual Op-Amp (TO-99 round metal case) still available from the USA on eBay -
> ...


I also have Lg V50, David, but the reason i have interest in the F2 is because my audiophile guru (who has a lot of expensiver gear, and experience) says that, despite the quality/price etc, the F2 is one of his favourite dac/amps (of any price) because it has an old-school analogue sound that is difficult to get these days. I'm not sure whether he has swapped the op amp or not.

Just this last week i performed my first op-amp roll on my Topping NX3S, and at his recommendation chose the old-school 5532p op amp.....and to put it mildly i've been blown away by what a $2 op-amp mod can achieve (the screwdriver i needed cost $5!!!!).....v-shaped, musical, just a delight!


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