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TSSA V1.6 docs and buyers list

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Hi Mike.

I have used the Panasonic FC for the last 7 years. They don't let me down regarding sound quality or life cycle.....

But i would advice to stick to LOW ESR and very important LOW ZL. It is important like ppm and tolerance of resistors.

Series inductance is now shown that often. But if you have to types with equally low ESR then look at the ripple current at 100KHz. high ripple current is better... Then you know that the construction is more rugged and stable..
 
Output impedance with ECX10P20 and ECX10N20 is 0.55Ohm. => Damping factor at 8Ohm is 14,5

with ECW20N20-Z and ECW20P20-Z , ALF16N16W and ALF16P16W and ALF16N20W and ALF16P20W: Damping factor is 24.

From my understanding of this circuit it would be possible to achieve some more OLG by increasing R7 & R8 to a higher value, e.g. 2k2, and then injecting more current from the mirrors.

This would increase damping factor but reduce stability but could probably be made to work very well for anyone who would like a bit more grip on the loudspeakers. Increasing the FB & gain resistors to 2k2 & 100 would probably restore stability to original levels.

I have not tried this except in spice in a similar circuit - so it is only a theory at present

Sonny, please correct me if this theory is incorrect.
 
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From my understanding of this circuit it would be possible to achieve some more OLG by increasing R7 & R8 to a higher value, e.g. 2k2, and then injecting more current from the mirrors.

This would increase damping factor but reduce stability but could probably be made to work very well for anyone who would like a bit more grip on the loudspeakers. Increasing the FB & gain resistors to 2k2 & 100 would probably restore stability to original levels.

I have not tried this except in spice in a similar circuit - so it is only a theory at present

Sonny, please correct me if this theory is incorrect.

No Mike. IT is correct. But the stability will be harder to control. But by adding more closed loop gain you reduce the effect on R7 and R8 again.
 
For all here in this thread.. I have made an error in the guide. Trimmer R22 should be turned CCW first before powering up.

After powerup bias is set by turning CW.

Hi Sonny, I noticed you did not change the master instructions yet for this point - would be very easy to miss this post and turn it on biased to 20A or similar !

So - I'm turning R22 counter clockwise - right ? and are we assuming the trimmers are originally set to midway point.

In other words - Do I just turn it fully counter clockwise before turn on ?
 
Hi Sonny, I noticed you did not change the master instructions yet for this point - would be very easy to miss this post and turn it on biased to 20A or similar !

So - I'm turning R22 counter clockwise - right ? and are we assuming the trimmers are originally set to midway point.

In other words - Do I just turn it fully counter clockwise before turn on ?

First of all, i have just uploaded a new manual where i have corrected it.

You are right turn the trimmer fully counter clockwise (CCW) before powering up.
 
My own amp ( DC linked fetzilla ) is fully run in and has good quality resistors in every position - the only trimmer is in the servo the o/p of that is filtered.

My implementation of TSSA 1.6 has Caddocks in FB & R32, R33 positions only and is not yet run in ( and I have to say that generally I really don't like the sound of a "new" amp ).

But despite this, I can hear that TSSA is doing some things very well. It has a very nice simplicity to the sound, an open natural quality that is pleasant to listen to. Voices sound very natural.

In some ways it sounds more open that my amp and in others it sounds more closed but now I have to allow everything to settle in before I really understand the full story of this design . . . . but I think my appetite for 2 stage amps has been whetted :)

p.s. using my simple choke supplies as shown elsewhere. No hum and almost hiss
 
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Well, if anyone here thought that the formula for retrieval of maximum detail was to take a reasonable topology and then increase OLG and FB then this amp may well disabuse you of your notion. ( as someone famous here once said )

My TSSA 1.6 CLG is 27dB, I think OLG is around 47db with my o/p devices so my FB is only about 20db ! - Sonny can you correct this if necessary.

I never heard so much detail before ! Sometimes today I was just laughing. It's quite holographic.

Sounded pretty dreadful during "run in". I think the worst is over now but I'll give it a few more dummy load silent "full on" sessions to make sure.

I remember someone once said that you never can match the detail of an o/p stage that is the VAS when you use a follower o/p stage. Also JLH noted that symmetrical designs tend to have a more detailed sound than SE ones - so with TSSA we seem to have a formula for ( almost ? ) maximum resolution of detail.

Might not be to everyone's taste and may not be ideal if you have cheap dac but this amp is certainly not lacking in the vitality & fun department !

more later . . .
 
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A SUGGESTED MOD

Sonny,

Listened quite a lot today and even though the sound was smoother now there was something about it that seemed somewhat surreal - somehow larger than life, exaggerated detail and over etched imaging - then, I played a particular track and realised - at least to my ears - something was not right - it just didn't sound natural.

So I did a mod that I always do on my designs but didn't want to do on this design until I had tried it in standard mode first.

I removed the PSU bypass caps and replaced them with epcos stacked film 4.7uF 100V caps in series with 0.2R ( 10mm lengths constantan resistance wire ). These caps are about the same size as the caps you suggested but are now mounted on the solder side of the board between the original ground pad and the pad where the pos & neg rails meet R32 & R33. ( I will post a photo when I have daylight tomorrow )

This mod eliminates a resonant circuit formed between the two caps and the inductance between them.

The amp is still stable. 10khz into 8R & 0.1uF looks more or less the same as before but interestingly, I think clipping is now a bit better than before.

I noticed a few days ago that the onset of clipping was somewhat asymmetrical on the negative cycle and when I checked again after the mod I thought it looked a bit more even.

My feeling is that subjectively this changes the character of the amp for the better. Before I made the changes the amp was making me laugh - after the changes I think it could much more easily make me cry and now all the the amazing qualities this design has seem able to flow more naturally.

I hope you try this mod and let me know what you think. I can send you constantan wire if you would like some, or give you the suppliers address.

I use this type of resistor for all low values for 2 reasons

1) it sounds very good
2) cost of each resistor is virtually nothing.

but I'm sure other good quality 0.2ohm resistors will sound good as well

The caps are available from Farnell.

that's it for now

cheers

mike
 
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Final comment before close of play . . .

Before I did the mod this amp sounded quite extraordinary but I noticed I relaxed more when I switched back to my DC linked fetzilla. Fetzilla gave less insight but was more refined & relaxed.

After the mod, and using my simple choke supplies, this TSSA 1.6 is the best amp I have ever heard by quite a bit margin. Now extremely insightful and quite refined.

I think there is still room for some more small refinements but already quite outstanding.

I now intend to do design a regulated supply - which I think this design will benefit from - and generally explore the whole field of 2 stage amps to the fullest extent possible.

Thanks Sonny - quite a masterpiece . . . You have opened up a new audio universe for me and I hope you enjoy the little suggestion I offer :)
 
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@Mikelm

There are C4,C5 470n bypasses on C2,C3 AC/DC split gain feedback electrolytics. Did you experiment on those too? Starting without any direct bypasses and then compare bypass solutions maybe its an acceptable practice also. I remember when I had been suggested to bypass my LCR 15000uF PSU capacitors in a JLH 80W amp with MKPs. The tone got pinched and I ditched them very soon. Snubbing is best but needs original PCB space. Your constantan wire does the trick neater though.

P.S. What speakers you got and how is bass with TSSA at ~20dB feedback?
 
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