Greetings back to you and thank you for the compliments.
The Williamson can make a nice amp, but requires very good output transformers to make it work without it oscillating. Not knowing the quality of the Chinese transformers makes this a gamble.
Using point to point wiring is fine.
Eli Duttman (see post above mine) is very knowledgeable and I would send him a private email on the subject and selecting a good schematic.
A Mullard topology would be better for you given the components you wish to use. This topology is more forgiving of the components, offers excellent fidelity, and is widely popular, which means you will have a greater set of resources at your disposal should you have issues or questions.
The Williamson can make a nice amp, but requires very good output transformers to make it work without it oscillating. Not knowing the quality of the Chinese transformers makes this a gamble.
Using point to point wiring is fine.
Eli Duttman (see post above mine) is very knowledgeable and I would send him a private email on the subject and selecting a good schematic.
A Mullard topology would be better for you given the components you wish to use. This topology is more forgiving of the components, offers excellent fidelity, and is widely popular, which means you will have a greater set of resources at your disposal should you have issues or questions.
Sure!
It is actually Eli Duttman. He uses that name for his user name, so just do a search on the forum for that name and then when you find one of his posts, click his name and send a private email.
Best of luck!
It is actually Eli Duttman. He uses that name for his user name, so just do a search on the forum for that name and then when you find one of his posts, click his name and send a private email.
Best of luck!
Sorry for the question : can you give me Eli Dutman's nickname ?
I don't find a post above yours cause yours is now first
Thank you.
Sorry, I do not. Give them a try. I bought a set of Chinese Ruby tubes (KT88s) to use to bring up the amp with the idea to buy better ones when I got the amp running. However, the Rubys work great, so I just kept them in the amp. Maybe yours will do the same? Give them a try.
Thank you, friend, I will do that !
By the way : do you have experience with Shuguang GEKT88 ?
Do you know other good KT88 ?
Thank you
Regards
Oh yes; beginners luck--experience is the art of making things fit to work.
I've never had stability issues with Williamson concepts, perhaps it's because I design out and understand the instability bugs. In each and every case I can obtain an extra 15dB on top of nominal 20dB global nfb headroom when instability sets in. I agree with Eli Duttman that the o/p trannies are the awkward spec items, but think there has been alot of misunderstanding and unfairness retro about Williamson designs.......I ought to do a demo, an amp wind-up on the most awkward speakers and blow the cones out. Sonically, the optimised design sounds relaxed, and has never let me down when the Vol is really wound up.
The winter project amp (bits gradually being accumulated) will be another power double 150W WILLIAMSON using Sowter output transformers.
My Citation is far more dodgy to alien speakers esp with long cables; and on this I always keep it at home.
Perhaps I ought to slot in a Hammond tranny in my power design and see what happens.
richy
Quick question about Williamson stability. Is the issue the additional driver stage and the associated phase shifts? In other words, if one chose an output tube with more modest drive requirements and used a tube with more "stones" for the PI and went stright from the PI to the output tubes would the stability issues be solved?
No thermal problems at all. The tubes are spaced well enough apart and it sits out in the open for all to see.
The bottom plate of the chassis has holes drilled into it and the four feet elevate that plate up off the surface. Seems to work fine in this configuration and I have run it continuously for hours on end just as pictured.
I should add that I have a lot of hours on this amp since it was put into service and zero issues. Rock solid, even with the Chinese Ruby KT88s, which I bought as a disposable tube in case the amp went poof.
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I'm hoping that someone will be quick to chime in and correct me if I am wrong, but I think that what you've described (phase inverter connected right to the finals) essentially describes the Mullard style topology that Eli referenced up above in reply #19. And yes, the Mullard is inherently more stable than the Williamson.
Mike,
Williamson topology uses a differential amp after the "concertina" phase splitter to obtain sufficient open loop gain. Remember, the 6SN7 has a μ of 20. Stage gain from the resistively loaded common cathode voltage gain section will be approx. 10, which is totally inadequate.
Yes, the phase shifts inherent to Williamson style circuitry can eat you alive. Really good (expensive) O/P trafos and tweaking the high pass pole freqs. is essential. Mullard style is (IMO) a better choice, when "budget" O/P trafos are to be employed.
Williamson topology uses a differential amp after the "concertina" phase splitter to obtain sufficient open loop gain. Remember, the 6SN7 has a μ of 20. Stage gain from the resistively loaded common cathode voltage gain section will be approx. 10, which is totally inadequate.
Yes, the phase shifts inherent to Williamson style circuitry can eat you alive. Really good (expensive) O/P trafos and tweaking the high pass pole freqs. is essential. Mullard style is (IMO) a better choice, when "budget" O/P trafos are to be employed.
I just bought a new amp a few days ago. It is something like the amp posted in this thread. It works well with my hifi speakers.
An externally hosted image should be here but it was not working when we last tested it.
I just found an interesting thread about the Music Angel KT88 on a norvegian forum :
AVforum.no - Drosler tilbake på Music Angel
They seem to have good ideas.
Could someone understand what it is about ?
And tell us ?
Thank you,
Regards,
AVforum.no - Drosler tilbake på Music Angel
They seem to have good ideas.
Could someone understand what it is about ?
And tell us ?
Thank you,
Regards,
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No, not the Mullard but the Dynaco ST-70. The inadequacy of the front end (a pentode feeding a concertina PS) has been addressed in very many after-market enhancement kits.
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