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Old 16th November 2012, 05:43 PM   #161
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Looking forward to your feedback Sakis, thanks for your contributions to audio
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Old 16th November 2012, 06:37 PM   #162
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Quote:
Originally Posted by Struth View Post
Hi Guys

Convention is not necessarily the best way. Leach had output stages oscillate to death with the zobel on the amp side of the coil. If you are tired of Leach, look at Bryston: they place the zobel after the choke, too. Chris Russell and Stuart Taylor are both very smart and tuned-in designers, as is Marshall Leach.

I think even Archie Leach would agree.

The trimpot for DC offset definitely will be problematic in its present position. The concern about performance is real. A less crucial facet is the fact both signal and DC currents are effected by the pot's rotation, so definitely adjust it WITHOUT a speaker in place - unless you like earthquake noises.

Considering the effort so far to create a power buffer with stupendous performance - wide bandwidth, super-low THD - it seems like a major fumble to retain the input offset trimpot. FdW and I seem in agreement on this, but Sakis will only consider Lineup's input for the PCB. His position is understandable considering his effort to design the card, but he has already acknowledged that this is only a beginning: more board designs will be necessary.

Have fun
Kevin O'Connor
Thanks Struth.
I think sakis should really listen to a few more fellows.
That can think of such I havent yet considered.
The whole idea with DIYaudio is to learn from eachother.

Here I post the current directives I have posted in EMAIL on his request.
Feel absolutely free to come forward to help us.
I feel we need a lot of assistance

Here you are:
Attached Images
File Type: jpg powerfollower28-PCB1.jpg (123.6 KB, 251 views)
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Old 16th November 2012, 07:23 PM   #163
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It works, but can you give a justification for this level of complexity, U5 and U9 could easily make up input stage and vas in a conventional design.
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Old 16th November 2012, 07:46 PM   #164
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To successfully drive this baby, you will need the brute force of a diamond input stage, however you could lower I1 and I2 by a factor of four and other options may open up
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Old 16th November 2012, 08:32 PM   #165
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Quote:
Originally Posted by OnAudio View Post
It works, but can you give a justification for this level of complexity, U5 and U9 could easily make up input stage and vas in a conventional design.
I see what you mean. This Buffer became more complex than I like.
But this is not unusual.
There are so complex preamplifiers for many dollars, when all that is really needed is one single OPamp.

The hunt for perfection costs a lot of complexity.
I can give schematics over amplifiers that are horrendous. Not at all on the level with Doug Self's Blameless.
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Old 16th November 2012, 08:33 PM   #166
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Quote:
Originally Posted by OnAudio View Post
To successfully drive this baby, you will need the brute force of a diamond input stage, however you could lower I1 and I2 by a factor of four and other options may open up
The input impedance is a around 23 kOhm.
An easy load for most preamplifiers or OPamps.
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Old 17th November 2012, 01:30 AM   #167
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Hi Guys

Complexity is in the ear of the beholder. If one wants a conventional design one should visit a different thread. The design here is actually NEW and INNOVATIVE! If that scares some people, they should hide behind Lin.

My PCB layout for my version of the buffer has all four elements of the diamond feedback buffer in contact. It is a simple matter to set the flats of the 2SA/2SC inputs back-to-back so they can be bolted together. The TO-92s are arranged outside of these with their flats against the TO-220Fs. A rubber band or heat-shrink tube can be used to hold everything in contact. Because of how the pinouts work out, the emitter Rs for the TO-92s must be mounted first, lying between the TO-92 and related TO-220F. No traces have to cross, so a single-sided arrangement can be used for this portion.

My PCB is 4.5x3", with two pairs of outputs, local filter caps and decoupling for the front-end. The addition of current sources for the front-end to make it exactly like the latest Lineup buffer would not make the board much larger if at all.

Have fun
Kevin O'Connor
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Last edited by Struth; 17th November 2012 at 01:32 AM.
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Old 17th November 2012, 09:03 AM   #168
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Thank you Struth.
Your posts are very helpful.
In fact you have been supporting this idea
all along the way.
I know you like the circuit.
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Old 17th November 2012, 09:37 AM   #169
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Struth.
Can you make a drawing of a Tube frontend for this buffer.
Use 6DJ8 in a single tube fashion.
You know the input impedance of the buffer is 22-23 kOhm.
The voltage gain should be like Gv=20 or less.

If you can not do it, I will do this myself.
I have in my SPICE a good model for 6DJ8.
It was actually made by M. Leach, the professor in electronics.
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Old 17th November 2012, 10:42 AM   #170
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Here are the figures
for Class A version.
Rails are +/- 25 Volt and quiescense current is 1.5 Ampere.
The clipping starts at 22 Vpeak. At 23 Vp it is heavy clipping.

The 20 kHz numbers are really good.
As can be seen from my analyse:
Quote:
Power Supply +/-25 Volt, 8 Ohm load TripleEF_5a Class A

THD 1kHz
04 Vp, 01 Watt THD 0.00006%
08 Vp, 04 Watt THD 0.00004%
12 Vp, 09 Watt THD 0.00007%
16 Vp, 16 Watt THD 0.00007%
20 Vp, 25 Watt THD 0.00010%
---
22 Vp, 30 Watt THD 0.16210%
23 Vp, 33 Watt THD 1.29898%

THD 20kHz
04 Vp, 01 Watt THD 0.00040%
08 Vp, 04 Watt THD 0.00080%
12 Vp, 09 Watt THD 0.00122%
16 Vp, 16 Watt THD 0.00166%
20 Vp, 25 Watt THD 0.00213%
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