300B Direct Couple SET Class A Design

In the past, JDM was opposed to using parallel tube sections in SE tube amplifiers due to a "subjective skew" he heard while using high efficiency horn speakers.

How would this design be an advantage over the SE KT88 mono amplifiers you have already built?

HB
The KT88 is 3 watts and the triple 6005 around 8+ watts.
 
Let’s do triple 6005 DC. I will do my own power supply design, power transformers, output transformers and you do your way. And you only need to share the actual two stage amp topology part (if you have permission). And then let’s compare our both builds. (No competition here to prove which build is superior but a just comparison of sonic outcome)

Just a wild idea. You may just take it with a pinch of salt…..
Let’s do triple 6005 DC. I will do my own power supply design, power transformers, output transformers and you do your way. And you only need to share the actual two stage amp topology part (if you have permission). And then let’s compare our both builds. (No competition here to prove which build is superior but a just comparison of sonic outcome)

Just a wild idea. You may just take it with a pinch of salt…..
@yogibear I may probably not built the 6005 nor shall I go ahead with the 300B unless I am able to sell my current monoblocks.

If you still wish to compare the sonic of both amplifier you are welcome to do so with my similar topology KT88 monoblocks. JDM says that the 6005 beats the KT88 by 20%. This can give you a fair idea.
 
The KT88 is 3 watts and the triple 6005 around 8+ watts.
With high efficiency transducers, 1W or less is often enough for nominal listening levels. 3W should provide adequate reserve power.

If you want to hear something different, add a switch that will allow you to listen to SE KT88 in triode mode.

You might need more bias current in the final stage to get enough reserve power in triode mode.

There are some options without having to sell the SE KT88 amplifier or build something entirely new.

HB
 
Hari, I hope you sell your 300Bs.

Not interested in KT88. F2a anyday over any bigger bottles.

6005 / 6AQ5 tube is quite musical hence was keen….
I don't have any 300Bs to sell.i am sure you have not listened to any DC KT88 before.
 
This project now is currently on hold until April next year. Actually I do not have an order to build this, but is more for fun and learnings. After building them, they may eventually get sold - if at all to clear up living space. Anyone keen can pre- book.
 
There is almost nothing better than having spare chokes at hand in case of need (unless one has to move)...it's been a long time since they depreciated and only seem to appreciate these years :)
 
Last week completed my single stage direct coupled, AC heated 300b amplifier driver stage design with EC91 tube. Operating voltage is 180vdc and operating current is 2mA. This will give me a voltage swing of 57volts and a voltage gain of 75 volts. The mu with this design stands at 90. Combined with the mu of the final tube gives a jump factor of 351 -a small fall from the magic number of 400. The plate dissipation of the finals is at 10.95watts.

This amp will start assembly after the completion of my ongoing 2a3 build project which is scheduled to be completed by March next year.

Thanks for looking.
 
I shall be looking for some adventure this month. I shall try and modify my current KT88 monoblocks to accommodate the 300B. For this i will need to change the Ea of the driver and the driver tube itself to EC91 (this is 7 pin). The 300B will be either my Shuguang 300B-98 or Psvance 300b-N after listening both. I have ordered a 5vac CT filament transformer for this duty. They will be AC heated. The direct couple voltage is calculated to be around 205vdc. Bias current is 48.5mA and grid bias around -37vdc. Plate dissipation i think is around 14.5watts. I have also ordered a 8pin to 4 pin adapter socket to save me from some mounting and removing work.

I am sure this will be a learning and fun.
 
Last weekend, i was able to complete one channel of the 300B and its been singing ever since for an average of 4hrs every day. I have owned the Dared VP-300b for over 6 years which was a 3 stage, capacitor coupled, DC heated amplifier.

Now in my new experience the magic of 300b begins with a 2 stage (jump factor of 400), direct couple and AC heated filament. There is no looking back and this is going to be my final amplifier for sure. I had earlier contemplated building a 2a3 and now after listening to the 300b in its new Avatar i may probably skip that idea.

The 2a3 to my ears sound very dynamic, open and musical where as the 300b sounds very organic, lush, accurate and natural. Its a more of what your own preferences are and i may lean more towards accuracy than the euphonic sound of the 2a3.

Even between the 2 tubes Shuguaug 300b-98 and Psvane 300b-n mesh plate, i shall prefer the shuguang over the Psvane because they are more organic and natural. The Psvane may have more grit but in the long run i shall prefer more natural sound. The Shuguang would have completed at least 7000hrs and the Psvane around 300hrs.


300b.jpg
 
When you are already 2-stage direct-coupled with a quick supply and mesh plates, all that remains is only OPT quality & personal preferences IMO :) Sincere congrats, nice work Hari! Did you leave the other channel KT88 to run for a while or is everything torn-down?
 
When you are already 2-stage direct-coupled with a quick supply and mesh plates, all that remains is only OPT quality & personal preferences IMO :) Sincere congrats, nice work Hari! Did you leave the other channel KT88 to run for a while or is everything torn-down?
The Other channel KT88 is still not torn down. I shall do an apple to apple comparison with the 300b tomorrow. I don't think it can outperform the 300Bs TBH
 
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