Audio Research VT100

[Olrum]

Hi to all!
I was very much involved with this amplifier in original sounding and there is a desire to repeat it, but unfortunately the full data and circuits on this product did not appear possible to find.
If there is an opportunity prompt where to find in high quality of the circuit.
The truth I nevertheless shall prefer target tube КТ88.
It is thankful in advance.


ARCDB - VT100

[mullardel34]

Originally Posted by Olrum

Hi to all! I was very much involved with this amplifier in original sounding and there is a desire to repeat it, but unfortunately the full data and circuits on this product did not appear possible to find. If there is an opportunity prompt where to find in high quality of the circuit. The truth I nevertheless shall prefer target tube КТ88. It is thankful in advance.


ARCDB - VT100

The link to the ARCDB Web page that you posted includes the full schematic (http://www.arcdb.ws/VT100/ARC_VT100_schematic_tn.jpg); what additional information are you looking for?

[Olrum]

There there is no information for a power unit. I understand what to think up simply, but to make a start it would be desirable from the original which is not present. Besides values of rating values in the basic circuit to consider very difficultly, even correcting software. And they are necessary for recalculation under possible replacement of the third cascade on 6N6 or 6N30. It is interesting to learn certainly parameters of target transformers though Hammond 1650T (W) quite for the beginning can be chosen from a series.

[LinuksGuru]

I looked at the schematic on the page linked from this thread. Yes, there are no PS unit shown, but you can use any suitable PS schematic with CLC filter capable of 350VA per channel and 420 B+ voltage.
As for resistors, 2W metal film will work fine.

[Cobra2]

I'm having one in for repair...but can not find type for Q1/Q2....(they have been sanded & painted...)

Arne K

[Olrum]

It is possible to think up a power unit it not difficultly, for example there are on a site other models with circuits of power units and besides is specified in the description power consumption. But it would be desirable for all таки to see his circuit .В to the basic circuit of the amplifier values of face values, instead of their capacity which can be accepted in 2 w are very bad visible. Except for that exact names of types of transistors are unknown...
This amplifier has surprised me not so much with capacity, how many speed and exact reaction to a pulse signal. In my opinion it is very successful model.

[mullardel34]

Originally Posted by Olrum

There there is no information for a power unit. I understand what to think up simply, but to make a start it would be desirable from the original which is not present. Besides values of rating values in the basic circuit to consider very difficultly, even correcting software. And they are necessary for recalculation under possible replacement of the third cascade on 6N6 or 6N30. It is interesting to learn certainly parameters of target transformers though Hammond 1650T (W) quite for the beginning can be chosen from a series.

Be cautious with your output-transformer selections when attempting to implement an Audio Research Corporation tube-amplifier design. In particular, ARC's "partially cathode-coupled" topology places unusual demands on the design of the output transformer. Please note that the ARC output-tube cathodes are directly attached to the output-transformer secondaries, forming a feedback topology that shares some characteristics with the McIntosh "unity-coupled" output-tube topology (but without the explicit/separate cathode-feedback primary windings of the McIntosh transformers). If the output transformer has insufficient bandwidth and/or too much inter-winding capacitance, the result is a high-power oscillator...

[Olrum]

Originally Posted by mullardel34

If the output transformer has insufficient bandwidth and/or too much inter-winding capacitance, the result is a high-power oscillator...

Yes I know about such moment and it strongly guards me.
Certainly it not McIntosh also is not present a separate cathodic winding, but also the negative feedback is insignificant all 6db, and I shall try to reduce her still as very much I do not like 6550 and I think more the best кт88 and кт66. Except for that application of linear Russian lamps GU-50 (LS-50)is possible. As capacity is not necessary for me 100 w, tubes will be on one in only two days off.
" Рartially cathode-coupled " and at me causes doubts... It seems to me that she is inefficient in connection with decrease in target resistance. Except for that regular transformers ARC I do not think, that strongly it is better Hammond...

[LinuksGuru]

Using secondary winding as part of cathode feedback is an el-cheapo cost-saving solution, think again, it even do not fully de-couples speakers from high-voltage supply rails! It the past it was used in middle-range Sansui AU-70 amplifier costed around $150 (this kind of schematic requires 2 center tapped secondary winding 2x8 or 2x16 Ohm, grounding 4 Ohm tap of standard 4/8/16 Ohm transformer is IMHO is even more ugly). Top-class Sansui AU-111 and some Revox amps had full-featured separate CFB winding.

[Olrum]

LinuksGuru


Probably you are right. But it is possible is connected and with indemnification of distortions at switching shoulders of the target cascade in class АВ, i.e. transition through 0. To me it too not so is pleasant .А to take a symmetric signal for NFB it is possible and as on the circuit.
It would be interesting to look circuits Sansui....