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Old 25th May 2012, 06:46 PM   #2541
brianco is offline brianco  Ireland
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Quote:
Originally Posted by igor0203 View Post
We should definetaly need one SSA/TSSA/CSA impressions thread. LC, you should also think opening LC Facebook fanpage
Absolutely, utterly no way! FB is the scourge of those who do not want synthetic, make believe 'friendship'!!

A new thread here on DIYaudio would help keep the technical apart from the pure listening experience. It would also be a good idea to break this thread into 2 sections, 1 covering the simplest version and the other covering the more full blown versions.
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Old 19th June 2012, 01:39 PM   #2542
Jay is offline Jay  Indonesia
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Default While Waiting For The Smart Guys

I have been long waiting for good high power amp utilizing Hitachi Latfet, and I have been hoping for the circuit to appear from SSA/TSSA thread.

But from a few circuits utilizing the latfet output, they are not very interesting because:

1) Low power (It seems that in TSSA topology the latfet cannot be operated at high power, and I couldn't solve the stability issues, but what the heck, IRF device works wonder. Ain't hexfets are so good at class-A!).
2) Not sufficient mosfet drive (Nico's version is the best among others but I'm not comfortable with simulated performance).
3) Not so good simulated performance
4) Not stable enough

Currently LC is developing the CSA, I think it is not latfet output but the old trusted BIGBT output. So I cannot wait any longer, I have to take the big risk () and design a latfet output SSA/TSSA

The reference/benchmark is a Goldmund Mimesis3 clone. So the SSA will also use 2 pairs of Latfet, powered from the same power supply and set with equal gain.

From preliminary design today, the SSA and Mimesis3 has equal simulated performance except:

1) SSA is much better at distortion. High order distortions have been reduced at the price of 2nd order (and overall) distortion, by increasing the output bias to around 400mA per mosfet.

2) Mimesis3 is much better at stability.

3) Mimesis3 is better at high frequency performance (especially my clone of the original). The best I have seen actually.

So for now I will take a break (have been sitting for hours) and post the distortion spectrum (Fourier chart) of Mimesis3 and the SSA:
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Old 19th June 2012, 02:44 PM   #2543
sonnya is offline sonnya  Denmark
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Give me 2 days, and you will have a 3 stage Latfet 100W TSSA amp in the same size as the one i have shown with 2 stages.

1) There will be no drive issues.
2) Low power (150mA idle)
3) No stability issues.

I have an amp here running with similar circuit which i can modify to a TSSA very easy.

- Sonny
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Old 19th June 2012, 03:09 PM   #2544
Jay is offline Jay  Indonesia
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Thanks Sonny. Looking forward to it.

Quote:
Originally Posted by sonnya View Post
1) There will be no drive issues.
I have a high standard with drive capability. To achieve that, three-stage TSSA is possible only with very high supply rail (I use 40V secondary to produce 56v56 for output and 75V for front end after voltage doubler/cap multiplier), and emiter follower of course.

Quote:
Originally Posted by sonnya View Post
2) Low power (150mA idle)
They say 170mA gives the lowest distortion but in my experiment, the spectrum is better with higher bias (higher overall distortion, higher 2nd order, lower high order distortions). With sufficient drive, no problem with 150mA.

Quote:
Originally Posted by sonnya View Post
3) No stability issues.
Cool.
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Old 22nd June 2012, 12:28 AM   #2545
Sheldon is offline Sheldon  United States
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Finally got this thermaltrak version in stereo and housed.

http://www.diyaudio.com/forums/attac...hermaltrak.jpg

Not as neat as LC's fabulous versions, but quite functional. The SSA amps are on the vero board at the rear of the chassis. The other two amps are symasyms - for a four channel amp (still need a set of binding posts and rca jacks for the symasyms). Early listening to the SSA shows no defects that I can hear. Clean, clear music, powering the range above 300Hz so far. I like it.

Technical: Gain of 23dB. No noise at all with 100dB+ speaker. Very slight low frequency blip at switch on (100mV offset, maximum). Not audible with my speakers. No audible blip at shut off. Offset wanders around for a minute or so, but settles down to less than 20mV. Nice square wave at 100kHz - slight, well damped overshoot with a load, a little more pronounced without.

Practical: It takes a while to tune in the bias and offset, as they are interdependent. Once done, it's stable so far. If I were building again, I'd adjust it close, then measure the 500R pots on the current sources. Then I'd replace with a resistor and 50R pot, as it's quite sensitive to small changes and takes some fiddling to get within 10mV. But I'm not highly motivated to order the pots and change now, as I've already done the fiddling. The input transistors are from the same batch and well matched within type, but no matching across types. The driver and outputs are not particularly well matched. They are what I had.
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Old 23rd June 2012, 11:08 AM   #2546
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Wink SSA by Sheldon

Quote:
Originally Posted by Sheldon View Post
Finally got this thermaltrak version in stereo and housed.
Hi Sheldon

Very happy for you, after many hours spent on SSA project, well-founded considerations, good work finally rewarded to you by enjoying the music.

Since you have four channels amplifier, you can also check to swap low-high amplification to see if vice versa combination is better and/or to go with same channels for both bandwidths.

Regards Andrej
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Old 23rd June 2012, 04:15 PM   #2547
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Quote:
Originally Posted by sonnya View Post
Give me 2 days, and you will have a 3 stage Latfet 100W TSSA amp in the same size as the one i have shown with 2 stages.

1) There will be no drive issues.
2) Low power (150mA idle)
3) No stability issues.

I have an amp here running with similar circuit which i can modify to a TSSA very easy.

- Sonny
How many hours nowadays day counts in Denmark? Daylight is surely longer but still 24 hours/day should be or is it?
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Old 23rd June 2012, 04:28 PM   #2548
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Sonnya, i am really looking forward to that version.
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Old 23rd June 2012, 06:18 PM   #2549
Sheldon is offline Sheldon  United States
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Thanks Andrej,

The mission for this amp is to power the horn for this speaker: Unity Horn Project Progress

Right now, the horn has a passive crossover internally, crossed with a DEQX to the midbass and low bass. I have a 4W SE tube amp that I've been using for the horn lately, and wanted something with a little more reserve to play with. The passive crossover in the horn is not ideal, but is corrected by the DEQX. I will either redesign the passive network, or more likely cross everything active. If I go completely active, the SSA/Symasym is a good candidate for the horn compression and mid drivers. My version of the SSA is well suited for this, as the low power requirement will not strain the VAS current capability of this three stage amp. The Symasym is probably better in higher current applications than this version of the SSA, so well suited to driving the mids, or midbass.

Right now, I have an 801 based SE parafeed amp driving the horn. It sounds good. The SSA sounds just as good.

Sheldon
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Old 25th June 2012, 11:01 PM   #2550
sonnya is offline sonnya  Denmark
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I have been working on the amps (testing).

But i am struggling to find the right solution for the TSSA AMP i promised. The following Will start a discussion.

I have three AMP here right now.

The TSSA , mirand modified, simple cfb AMP.

The mirand and simple cfb AMP shares the same topology and Sub -3dB point. The mirand is an bjt's output stage. The simple cfb AMP is an lateral fet output type. Both "EF" types.

basicly those two AMP should have the same bas reproduction. But that is not the case. The lateral AMP is a bit lower level in perception, and less detailed. There is information missing.

But the TSSA which is a Drain output type does not miss level.

I now a lot Will not agree with me. Some would say that this is not the case with pass amps. But they are actually Drain output types. (aleph)

We are now 4 Independent people saing the same here in Denmark. Sourcefollower lacks precision and level in the Sub region.

But Drain follower Will be tested wednesday by two more. But until now we are two saying that it does not lack precision and level.

Maybe i Will end up with a 100watt TSSA 2 stage AMP.
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