(AK) classA HA/Preamplifier.

[Deleted]

So here is the Mule build

I’ve used ¼ jacks for IP/OP



I’ve also hooked in some RCA sockets to allow pre amp use. The RCA are disconnected when the ¼ inch plugs are inserted which is kind of convenient and will make things easier when hooked up to my Opus/Ventus (about to become IVY3) build.

So the etched boards should allow easy swopping in of components and not be tooo difficult to replace should I damage one in the process.

I’ve used the old 150R LS352 emitter resistor values as I’m interested in hearing what difference the new 200R makes to the sound. I have SF14 diodes in place and all balanced out nicely along with ridiculously low DC offset on the OP.

Take care

[Deleted]

Apr 2, 2013 13:58:15 GMT @shaun said:

Hi Alex

Yes point taken on the number of transformers but Will was good enough to leave space for them so I thought why not.

I will try taking them out to hear if that makes a difference though as they are really only in out of habit.

That 470nf cap (should read 470pf) was a typo sorry Martin for any confusion caused. I’ve gone back and edited it but I must take more care when posting component values.

Take care

Hi Shaun
As I wanted to use mine in a 1U rack case, I used the smaller SC PSU PCBs, but needed to fit a couple of diodes under the PCB due to the filter electros being fatter.
It is possible that I fitted the 470pF under the PCB too, but I would need to lift them out to check. I will do that after I get the 6 monthly rental property inspection
out of the way. If you don't notice an improvement I won't bother.

Kind Regards
Alex

[Deleted]

Apr 2, 2013 20:52:05 GMT @sandyk said:

Apr 2, 2013 13:58:15 GMT @shaun said:

Hi Alex

Yes point taken on the number of transformers but Will was good enough to leave space for them so I thought why not.

I will try taking them out to hear if that makes a difference though as they are really only in out of habit.

That 470nf cap (should read 470pf) was a typo sorry Martin for any confusion caused. I’ve gone back and edited it but I must take more care when posting component values.

Take care

Hi Shaun
As I wanted to use mine in a 1U rack case, I used the smaller SC PSU PCBs, but needed to fit a couple of diodes under the PCB due to the filter electros being fatter.
It is possible that I fitted the 470pF under the PCB too, but I would need to lift them out to check. I will do that after I get the 6 monthly rental property inspection
out of the way. If you don't notice an improvement I won't bother.

Kind Regards
Alex

Hi Alex

I’ll have a play with that cap over the next few days and see if I can hear a difference.

The really gratifying thing is that after 3 builds of your Class A HA/PRE I hag had consistently fantastic results.

So no fluke just good design

You may have noticed that the Mule build has a polystyrene IP cap instead of the polypropylene. I only had 100pf in the strene but it sounded quite nice and I’ll be trying a 47pf soon. Not a huge change in SQ but just a little sweeter IMHO compared to the build that I have in Will’s lovely boards.

I may try silver mica next just for completeness.

I know that the polystyrenes are not to everyone’s taste but I kind of like the ones that I have in that spot.

Take care

[Deleted]

I know that the polystyrenes are not to everyone’s taste but I kind of like the ones that I have in that spot.


Read more: rockgrotto.proboards.com/posts/recent#ixzz2PLTianLE

Hi Shaun
I like polystyrenes too, but if I don't have one in the needed value, but have some in MKP, I will use them.
I have a couple of 39pF Silver Mica but have yet to find a place for them.
Playing around with those 3 types in the 68pF compensation capacitor could be an interesting exercise, but not with the finer tracks on Will's PCB
where too much playing around may cause damage. I have seen reports that you can sometimes get away with SMs of slightly lower capacitance in those areas.
You would need to check with a function generator on square waves, and use a CRO to check for overshoot.
Kind Regards
Alex

[pingu]

Thanks to both Alex and Shaun,

your comments taken on board and changes noted. When I get the caps for the PSU and power up I'll let you all know how it goes.
When the smoke has cleared of course.

Looking forward to the SC HA project mmmmmmm

John.
Amazing work I will never get to that level very well done

All the best
Martin.

[jonclancy]

Hi Guys,

I may be being thick, but it might be worth Skyping Texas Components direct in the USA for prices. Charcroft say they make their resistors in the UK - I assume they get the bulk foil material from Israel (where it's produced, I think). Shaun, thanks for blazing a trail here!!! If Charcroft are too pricey in those values, you may consider Caddocks etc as well. I've used them in the past in DAC builds etc.

Martin, thanks for the kind words. I can tell you that only recently it would have had nails sticking out of it. Just a bit of practise and experimentation, and some specific and reasonably inexpensive tools will see you right. We posted some howto article on fabrication on the Grotto, somewhere!!

Here you go:

rockgrotto.proboards.com/thread/6417

The first post date shows how long this particular project has taken...

[Deleted]

If Charcroft are too pricey in those values, you may consider Caddocks etc as well. I've used them in the past in DAC builds etc.

Hi Jon
The only place I would ever consider using those obscenely expensive resistors would be in the input terminating, and feedback resistor locations.
Even then, they would likely be a waste of time unless you were using a far better than average source, and source material.
Kind Regards
Alex

[Deleted]

Apr 2, 2013 22:00:34 GMT @sandyk said:

I know that the polystyrenes are not to everyone’s taste but I kind of like the ones that I have in that spot.


Read more: rockgrotto.proboards.com/posts/recent#ixzz2PLTianLE

Hi Shaun
I like polystyrenes too, but if I don't have one in the needed value, but have some in MKP, I will use them.
I have a couple of 39pF Silver Mica but have yet to find a place for them.
Playing around with those 3 types in the 68pF compensation capacitor could be an interesting exercise, but not with the finer tracks on Will's PCB
where too much playing around may cause damage. I have seen reports that you can sometimes get away with SMs of slightly lower capacitance in those areas.
You would need to check with a function generator on square waves, and use a CRO to check for overshoot.
Kind Regards
Alex

Hi Alex

The change that I noticed was not huge and certainly not enough to tip the sound balance (if they had I’d take them out) but every little helps IMHO.

You are spot on with the 68PF comp cap which looks like a good place to start with the same value of silver mica.my only reservation about the silvers is that they can sometimes sound a little hard used in the wrong spot.

On the Charcrofts

Yes they are outrageously expensive and may make no difference what so ever but I’ve been interested in trying some in the spots that you have identified since my first build. There are cheaper alternatives like the Vishay box type that I’ve used before and I’d have to say that they were good in a phono stage build.

So it's suck it and see

I think that the mule build will make for a much less stressful test bed as I’m nervous of messing up Wills nice boards.

Hi Martin

''Amazing work I will never get to that level very well done''

Yes you will it's just practice and help from others.

We have no super humans here just people who like to share.

We tend not to use the S word tooo often and I’m confident that your PSU build is going to be fine. Just be careful to get the = & - regs in the right spots (yup done that before).

Keep us posted on the PSU.

You will soon be marvelling in the sweet sound of Alex's HA/PRE.

Hi Jon

Not blazing a trail just a little unfinished business.

I agree with Alex that the source component is important but from what you have I’d say that's not going to be an issue.

Circuit and SQ wise I’d agree with you that Alex’s PRE/HA is about as good as it gets.

But I’m only advocating a little light breathing on and no more than that. just in the Interests of scientific research.

I have the 10K FB resistors to hand so the mule is going to start carrying them soon.

I’ll keep you posted.

Take care

[Deleted]

The change that I noticed was not huge and certainly not enough to tip the sound balance (if they had I’d take them out) but every little helps IMHO

Hi Shaun
I checked my HA about 30 minutes ago,
I have 470pFs mounted across the secondary windings under the PSU PCBs. I am using Panasonic FC 2,200uF 35V in the PSUs,
and Suntan CD286 2,200uF 10V in parallel with Suntan 2,200uF 16V on both sides of the JLHs.
I am using polystyrene caps at the input , and most likely 47pF as I am using a 50K DACT2 volume control.
The compensation capacitors are 68pF polystyrene .
Kind Regards
Alex

[Deleted]

I agree with Alex that the source component is important but from what you have I’d say that's not going to be an issue.

Hi Shaun
An interesting aside here, Funny things can happen when you are using digital sources.
With my present set up, I am using an old Oppo 981 connected via coax SPDIF to the SC DAC, as well as HDMI from the Oppo to the LED TV for the video side of things.
The LED TV is connected via Toslink to another input on the SC DAC. . The SC DAC is connected to Input 1 on the Class A preamp, and as well, the analogue out from the Oppo was connected to Input 2 of the Class A preamp.
Both the active side and the earth side of all inputs are switched in the preamp to prevent more than one SMPS device from degrading overall performance due to high voltage at low current leakage from SMPS devices coming in on the earth side of the preamp, to IEC earth at the power amplifier.
Unplugging the analogue out from the Oppo at the Oppo itself, gave a quite noticeable improvement in focus and SQ from both DTV from the TV,
AND CD playback from the Oppo 981, via the SC DAC !
I have now removed that cable to the preamp, as audio from the Oppo via the SC DAC is vastly improved over analogue out from the Oppo anyway.
Kind Regards
Alex

[Deleted]

Apr 3, 2013 10:53:55 GMT @sandyk said:

I agree with Alex that the source component is important but from what you have I’d say that's not going to be an issue.

Hi Shaun
An interesting aside here, Funny things can happen when you are using digital sources.
With my present set up, I am using an old Oppo 981 connected via coax SPDIF to the SC DAC, as well as HDMI from the Oppo to the LED TV for the video side of things.
The LED TV is connected via Toslink to another input on the SC DAC. . The SC DAC is connected to Input 1 on the Class A preamp, and as well, the analogue out from the Oppo was connected to Input 2 of the Class A preamp.
Both the active side and the earth side of all inputs are switched in the preamp to prevent more than one SMPS device from degrading overall performance due to high voltage at low current leakage from SMPS devices coming in on the earth side of the preamp, to IEC earth at the power amplifier.
Unplugging the analogue out from the Oppo at the Oppo itself, gave a quite noticeable improvement in focus and SQ from both DTV from the TV,
AND CD playback from the Oppo 981, via the SC DAC !
I have now removed that cable to the preamp, as audio from the Oppo via the SC DAC is vastly improved over analogue out from the Oppo anyway.
Kind Regards
Alex

Hi Alex

Yes I agree that those SMPS can have can affect SQ and suspect that the sort of HF garbage those things spray out has more than a little to do with that.

As you say people are now beginning to realise that human hearing is much more complex than first imagined.

Which leads me on to resistors?

I remember reading Morgan Jones Valve amp design where he mentions the effects of resistor:

Self-noise

Inductance

Magnetism

(No black magic involved)

And thought what rot.

Then I tried some Audionote tantalum resistors in one of my Valve builds and well what do you know I could hear the silence.

But

I think such components need to be used where they do the most good IE

As you have stated

In the FB loop and IP but I’m also thinking that the overall gain of the device may magnify the effects of those sort of resistors in the same way as it does noise

So let's see what gives

Take care

[Deleted]

Hi Shaun
What does a magnetised resistor sound like ?
Describe it without using that 4 letter word starting with "S" and ending with "T"
TBH, I think that the recent thin film resistors should be pretty good there, but they are normally surface mount devices.
BTW, back in the Morgan Jones valve amp days, didn't they mainly use the noisier carbon composition resistors ?
In the hey day of valve amplifiers, metal film resistors weren't around, were they ?
Regards
Alex

P.S.
Good Night from Sydney Au.

[Deleted]

Apr 3, 2013 11:49:19 GMT @sandyk said:

Hi Shaun
What does a magnetised resistor sound like ?
Describe it without using that 4 letter word starting with "S" and ending with "T"
TBH, I think that the recent thin film resistors should be pretty good there, but they are normally surface mount devices.
BTW, back in the Morgan Jones valve amp days, didn't they mainly use the noisier carbon composition resistors ?
In the hey day of valve amplifiers, metal film resistors weren't around, were they ?
Regards
Alex

P.S.
Good Night from Sydney Au.

Hi Alex

I’m not sure what a magnetised resistor sounds like I just know from experience with my own ears that the ones I’ve tried that where nonmagnetic sounded better in the places I’ve tried them. So one or all of the above preperties may have made a difference IMHO.

And that’s the ear test for me:

nope Morgan Jones recommends Metal film where ever possible due to the lower self-noise of those units but then MJ is a slightly more free thinking modern designer in that and many other respects.Tantalum resistors are even lower noise than most standard metal films so could be that self-noise does influence SQ in some way but the usual drawback is that they cost more and sounded great on the IP tube cathodes of my builds.

MJ provides a list of noise figures for each type of resistor in his books BTW and they are a great resorse for DIY tube builders.

Still if I try and don't like well I’ve learned something so all good.

And a grey and overcast G'day from the UK

Take care

[jonclancy]

Vishay S102. Yup, that's it.

I am a fan of the TX2575 and it's brothers, for a few reasons. MF are good, but you can up the ante (realistically) with considered use of those parts. CTC specified them in the Blowtorch.

:heh - wait for the hits!!:

[Deleted]

Apr 3, 2013 22:25:14 GMT jonclancy said:

Vishay S102. Yup, that's it.

I am a fan of the TX2575 and it's brothers, for a few reasons. MF are good, but you can up the ante (realistically) with considered use of those parts. CTC specified them in the Blowtorch.

:heh - wait for the hits!!:

Hi Jon

Yup those are the ones that I’ve tried in a few of my builds mostly on the front end and have usually been pleased with what they do.

For something a little less expensive those little Welwyn (Vishay) (rabbit poo ones) work well enough and yes I agree no scatter gun needed just a careful selection of locations.

Take care

[Deleted]

Hi All

Just a quick update on the Charcrofts.

I have the 10K resistors to hand and am just waiting on the 56K and 220R input resistors which I’d like to solder in first just to have some idea of what’s happening with each change.

Expect some news over the next week or so.

Hopefully I’ll feel totally cleansed by the experience

But who knows.

Just as an aside

My Daughter and two year old grandson (headphones really useful) recently visited and asked for a listen to Alex’s HA/PRE.

So I plugged in the K701 and took her for a spin.

She really loved the sound and commented on its ability to portray all of the music without exaggerating any of the frequencies. Loved the bass but appreciated its uncoloured naturalness and un-boomy quality. She thought that it sounded just great and errrr well ‘’can I have one for Xmas dad’’ was the end result.

I really must stop letting guests hear Alex’s amps

it's causing me toooo much work

Take care

[Deleted]

Hi Shaun
Probably best to let only sons and daughters have a listen ?

Kind Regards
Alex

[Deleted]

Apr 3, 2013 9:43:56 GMT @sandyk said:

The change that I noticed was not huge and certainly not enough to tip the sound balance (if they had I’d take them out) but every little helps IMHO

Hi Shaun
I checked my HA about 30 minutes ago,
I have 470pFs mounted across the secondary windings under the PSU PCBs. I am using Panasonic FC 2,200uF 35V in the PSUs,
and Suntan CD286 2,200uF 10V in parallel with Suntan 2,200uF 16V on both sides of the JLHs.
I am using polystyrene caps at the input , and most likely 47pF as I am using a 50K DACT2 volume control.
The compensation capacitors are 68pF polystyrene .
Kind Regards
Alex

Hi Alex

Yes that's more or less what I have

I had 47pf Wima polypropylene on the IP but changed to polystyrene which I liked a little better in that spot. For the mule I’m using one of those Vlab 50K log jobbies which is not bad.

By the way Vlab seemed to have upped their game with the SMD resistors now mounted on wafer boards which makes for a sturdier unit with less CLICK when switching.

Not as nice as our DACT units though.

‘’Probably best to let only sons and daughters have a listen’’

Yes I agree but when something special like this turns up its hard not to share it (a little)

Take care

[Deleted]

Hi All

An interesting day at the errr hoffice

The remaining Charcrofts arrived this morning and well I just got that itch, you know the one that needs to be scratched and put the front end 220R and 56K in and had a listen.



OK

Before I start I’d just like to make a few points.

This is not in any way meant to be a redesign of Alex’s superb PRE/HA just a light tweak to satisfy my own curiosity. Alex’s Amps are IMHO outstanding and need no such redesign but because of my absolute faith in his amp as is I wanted to push things a little further to see what gives.

A word on the ‘’sound’’ of resistors.

So say that all resistors sound the same which is a fair point but does not match my limited time playing with them. I’ve tried most tryes of resistor such as Tantalum, Holco MF, carbon film and composite and of course the Vishay bulk foil types to name but a few. IMHO and experience they all sound quite different but this also depends on where they are used.

So the following IMHO in my setup with my ears.

So after the usual warm up for the Mule and my original HA build with the Opus/IVY3/K701 (easier to set up for simultaneous testing).

Mmmm interesting

TBH before the Charcrofts went in to the mule, my original build sounded a little better. Note sure why but I suspect that the originals DACT compared to the Mules Vlab switch pot.
But now the Mule has turned into a race horse.

Yup sounds noticeably faster transient wise which is most noticeable in the Bass which has increased in tunefulness and seems to go just a little lower. The charcrofts also seem to sound cleaner and clearer with a much more Technicolor presentation which almost makes the mule sound a little louder by comparison (go figure). The head stage is ‘’bigger’’ compared to the original and the top end really extended and sweet without any of the glare that some resistors can bring. Not that the original was any slouch in that respect but the Charcrofts do sound better in a less than subtle way IMHO.

fine detail is also much better resolved and clearer. (if that makes sense)

AIR –MOON SAFARI-SEXY BOY just because I like it and know it well. There’s a kind of faint wha wha sound going on in the background which I’d heard before but hold on it’s a vocoder. Nope not dug far down enough to notice that before.
So I stuck the 10K FB resistor in and more of the same SQ wise



In a word the Charcrofts sound delicious.

Just to be clear

The sound balance has not changed and it still sounds like the Class A I’ve come to know and love. but IMHO the carcrofts really squeeze the last drop out of Alex’s wonderful HA/PRE.

AND

Would I feel embarrassed if the charcrofts made no difference or sounded worse?

Nope they are expensive units no doubt about it but I learn by hearing for myself and would say so if they were crap. People may have noticed that I try to report only on what I’ve heard for myself and leave the speculation to others.

Worth the money welllllll

depending on the rest of your systems possibly so but mine are staying that’s for sure. I’m pretty happy with what they do and plan on trying some in Alex’s PA now my apatite has been wetted a little.

Anyone looking for a slightly less expensive Resistor to try could look at the Vishay Bulk foil units. I’ve used them and liked them much. I’ve not tried them with Alex’s HA/PRE but they look good for experimentation.

I’ll be trying the Mule as a pre in my room system next which should be interesting.

Take care

[Deleted]

Holy resistance Shaun!

Looking at the HiFiCollective price list (on a slanted view, just like Batman's villains hide-out), the three resistors come out at a whopping £90 (quite a percentage of overall build cost) per stereo amp , yep, that's a scream of pain for each one

Knowing you're a big valve fan, would you say these resistors have added a valvey (if that's a word) sound? A softer tone? A mellowness?
etc. etc. ?

For you, was the cost fully justified?

[Will]

Hi Shaun,

Your home-etched racing mule looks fab!! Reminds me of mine

I'm really interested in your resistor adventures, as I'd given a little thought to the types you are using when I did the AKHA pcbs.

I made provision for the Texas foils to have their own 'holes' on the pcb for the resistor that is in series with the input signal and also the output resistor. If you look on the PCB, you'll see an extra set of holes, so it would be easy to snip of the existing MF resistor and the foil types will drop in. The feedback resistor was difficult to provide for without constricting the earth strip down the center of the PCB, so that'll need more care.

[Deleted]

Hi Shaun
Interesting findings. Many will say that this kind of thing can't possibly be happening, but then neither should many of the things that I have reported hearing.
I won't be going there this time though, as it's starting to get a wee bit outside my means.
Yesterday I had my preamp on the bench, wondering what little thing could be further improved. I found that the banana socket that I fitted to facilitate connecting a lead between the case of the preamp and the case of the 15W Class A had a few ohms resistance between it and the other earthed points.
It was in the corner of the case , and banana sockets aren't always the easiest things to fully tighten up, especially in locations like that .
I then ran a short wire from it's solder tag to an adjacent good earth point .
Even DTV sounded a little better again. Almost everything you do at this stage of development appears to be noticeable.
It is worthwhile checking to see that all earth points read the same very low resistance to the main earth . That includes the bonding of other metal panels together too
Kind Regards
Alex

[Deleted]

Apr 9, 2013 18:29:10 GMT @cjarchez said:

Holy resistance Shaun!

Looking at the HiFiCollective price list (on a slanted view, just like Batman's villains hide-out), the three resistors come out at a whopping £90 (quite a percentage of overall build cost) per stereo amp , yep, that's a scream of pain for each one

Knowing you're a big valve fan, would you say these resistors have added a valvey (if that's a word) sound? A softer tone? A mellowness?
etc. etc. ?

For you, was the cost fully justified?

Hi Chris

Nope I’d say that the tone remains unchanged just better focused, clearer and more vibrant. A bit like stepping out into the sunlight on a bright summer’s day (almost poetry)Same scenery more light

As to valve sound well I’m a big fan of good sound however it's delivered and Alex's amp delivers. Now tubes don't have to sound warm and cuddly either but much of that also depends on the PSU used and the circuit.

One thing that I’ve learned from Alex is that Transistors are capable of top quality sound in the right hands just as much as tubes can sound bad in the wrong ones.

OK no one would pretend that these resisters are cheap nope not even me but believe me I’ve spent more on two caps so it's not so hard for me to get my head around.

Secondly these resistors are used in some pretty expensive gear which I’d never have the chance to listen to otherwise. But the cost implemented in Alex's amp is a real bargain considering what you get SQ wise which is at the heart of what i think DIY should be about. Top sound without the crazy price tag.

How much would Alex's amps be to buy commercially? Big money and even more with the DACT and a few fancy Dan resistors.Cost justified for me yes but that's just a personal opinion and satisfied my curiosity

''Hi Shaun,

Your home-etched racing mule looks fab!! Reminds me of mine

I'm really interested in your resistor adventures, as I'd given a little thought to the types you are using when I did the AKHA pcbs.

I made provision for the Texas foils to have their own 'holes' on the pcb for the resistor that is in series with the input signal and also the output resistor. If you look on the PCB, you'll see an extra set of holes, so it would be easy to snip of the existing MF resistor and the foil types will drop in. The feedback resistor was difficult to provide for without constricting the earth strip down the center of the PCB, so that'll need more care.''


Hi Will

How’s it going?

Those boards are pretty much off of the original art work that Alex was kind enough to send with your LTP mods incorporated. The Offset corrector is my own work with the PCB software I scored from Maplins and my 3rd effort on that front so getting better all the time. I managed to add the extra capacitor across the 1m FB resistor that Alex had recommended which was nice and easy.

I notice the spacing’s for Bulk foils in the locations that you’ve mentioned but wanted to try out with FB resistor in place so went with the Mule. I also wanted to try some polystyrenes on the 47pf IP which are worth the effort and expense and have something to compare to also as we have such flea like audio memories apparently.

Having the Mule is a good way of protecting the main deal so a no brainer.

how's your HA/PRE build comming along?

The foils for the Texas resistors are provided by Vishay as are the ones for the Charcrofts and then laser cut to value by the recipientso no reason to suppose that they will sound different.(Charcroft and Texas are Vishay distributors) But some of that is going to depend on production methods. I did look hard at the Texas as they are less expensive but add in shipping and import/handling fees and the cost difference narrows somewhat.

What we need is a friend stateside who would be willing to set up a purchase and send on to members as we may avoid such inconveniences.

Hands across the water anyone?

Take care

[Deleted]

Apr 9, 2013 21:58:17 GMT @sandyk said:

Hi Shaun
Interesting findings. Many will say that this kind of thing can't possibly be happening, but then neither should many of the things that I have reported hearing.
I won't be going there this time though, as it's starting to get a wee bit outside my means.
Yesterday I had my preamp on the bench, wondering what little thing could be further improved. I found that the banana socket that I fitted to facilitate connecting a lead between the case of the preamp and the case of the 15W Class A had a few ohms resistance between it and the other earthed points.
It was in the corner of the case , and banana sockets aren't always the easiest things to fully tighten up, especially in locations like that .
I then ran a short wire from it's solder tag to an adjacent good earth point .
Even DTV sounded a little better again. Almost everything you do at this stage of development appears to be noticeable.
It is worthwhile checking to see that all earth points read the same very low resistance to the main earth . That includes the bonding of other metal panels together too
Kind Regards
Alex

Hi Alex

People are always going to have their own opinions on the sound (or not) of caps/cables/resistors and so on. I have an opinion and there are as many others as there are ears.

All good IMHO and the more the merrier

That’s how we learn

I agree with fitting binding posts and I’ve done that with all of my builds of your amps. I found that with the DACT fitted I had a little of that not earthed zzzzzing without making the connection between PSU and case. But not so with the new improved Vlab unit so yes it all matters. Good earth bonding is also a must for this type of gear and can make all the difference SQ wise.

funny after 79 pages of the most interesting and educational post's that I still have a read through when I have time.

This Amp just rolls on and is still developing which is just great DIY and super for SQ.

Well done

Take care

[Deleted]

Nope I’d say that the tone remains unchanged just better focused, clearer and more vibrant.

That's the answer I was afraid of

I need to get these little babies built up ASAP...