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Old 18th May 2012, 09:53 AM   #21
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I just wanna know, how does it sound, really?

Is it really musical and visceral?

Or does it "do" good music in a wierd way?

Or when you listen to you ou get fatigued and
that funny head ache and ear ache from someting
that just isn't right?

Cheers,

Sync.
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Old 18th May 2012, 09:56 AM   #22
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Who are you asking to?

Best regards!
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Old 18th May 2012, 10:37 AM   #23
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I think push pull should be considered since it would be much easier to get a full bandwidth output transformer without saturation problems, and then, besides supporting class A, it could have a switchable or semi-automatic energy/tube-life saving mode where it could run in class AB, turn off some of the tubes, or perhaps have a controller dynamically adjusting bias current to track power requirements. It could use a combination of an internal clock/calendar and ambient temperature sensor to be more aggressive with energy savings during summer and less when the heat generated would be useful. When running many tubes in class A at more than half rated dissipation, some quiet fans blowing air past the tubes would greatly extend life.

One of the more exotic shunt regulator designs on this site could be used for the screen supplies in an optional pentode mode, and with minor modification a pair of them coupled to the OPT in push-pull, with the reference modulated with audio to provide a fallback solid-state amp function for the lowest energy mode. It could provide for continuous function while the tubes are waking up from cold-sleep mode, for nighttime use with limited battery reserves from a solar power system, or perhaps when using less demanding inputs such as non-musical television programming or streamed content. Being able to adapt and provide suitable energy modes for a wide variety of conditions while providing excellent audio at all times would make it very unique, and a more responsible choice for current global conditions. Otherwise, I don't see too much point in putting a lot of effort into yet another costly great-sounding toaster that burns considerable energy and eats tubes as if they were plentiful. There are plenty of solid designs of that type already.

There might be a market for an energy-intelligent high-fidelity amp in Japan. With all of the 50 remaining nuclear plants shut down for the first time in 42 years, people are being asked to cut usage to avoid outages. The weather turned warm yesterday which increases power demand. Some unusual products have appeared, such as a television that charges a battery at an off-peak usage time so it can run without external power during high demand or outage periods.

Last edited by riccoryder; 18th May 2012 at 10:45 AM.
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Old 18th May 2012, 12:03 PM   #24
AJT is offline AJT  Philippines
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Quote:
Originally Posted by SyncTronX View Post
I just wanna know, how does it sound, really?

Is it really musical and visceral?

Or does it "do" good music in a wierd way?

Or when you listen to you ou get fatigued and
that funny head ache and ear ache from someting
that just isn't right?

Cheers,

Sync.

this is the first time for me to hear a non global negative feedback power amp.....although there was a provision for it i decided at the last minute not to use it....i was rewarded.....

later on the owner took the amp to a listening session for 3 hours straight and had those who heard the amp had nothing but praises...

big tube amps can really push speakers around.....this Jolida wannabe can really sing and play the drums as though it was real...

this 211 power amp monoblocks packs a wallop, although not done by me, it landed on my doorstep due to some humming issues, after i fixed it, all was great...
Click the image to open in full size.
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Old 18th May 2012, 12:05 PM   #25
chrish is offline chrish  Australia
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For the power levels you require, I would think that push-pull is a sensible choice. Your other design considerations - class A, no feedback, KT88, triode mode, may be limiting your options. If you now think 30-80 watts is your goal, there are many designs that might suit. Are the design requirements based on perceptions or experience? The reason I ask is that you may want to try experimenting with something like Pete Millett's driver board Push-pull driver board and see (hear?) different topologies to determine what your preferences really are. You may find that you prefer a little more power from ultra linear or happy with less power but triode etc. When you find what you like, you can finalise the design - or you can keep tweaking
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Old 18th May 2012, 12:08 PM   #26
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For more than 2 tubes an output transformer can be expensive. To a great extent the quality and sound of a tube amp depends entirely on the output iron. So that is almost your first consideration before anything else.

Jadis made commercial amps they had 8 x 6550 per channel... not so rare.

ZFB and class A is nice, but runs hot. Maybe worth it.

Go for it, enjoy the quest!

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Old 18th May 2012, 12:09 PM   #27
AJT is offline AJT  Philippines
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Quote:
Tony, I really like your project. A separate PSU when going so big is an interesting approach. I would have gone with a closed enclosure. Coming from the SS world, one thing surprises me is the common tube builders approach of placing components outside the case. I can understand it's done for valves for heat reasons, but seems to me that its too far common to place other unnecesary (and dangerous!) components outside the enclosure. For example, in your desing, I would have gone with the PSU in a closed case. That way it seems less obscene, fragile, and the tube module can be piled on top of it. But that's just my side of view
Great and impressive design all in all!
i started doing tubes in the 70's, raising family and working overseas, i stopped dabbling in tubes, but my SS adventures went on....so now that all my kids are earning their own money after finishing college, i have more time to do tube projects now....

the amp used 3 umbilical chords, i made sure that there is no way that they will be hooked up the wrong way...i used amphenol connectors of different sizes.....
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Old 18th May 2012, 12:22 PM   #28
Cassiel is offline Cassiel  Libya
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Regiregi, there's nothing specially difficult about designing or copying a circuit for your amp. The trouble is the output transformers. To get great sound you will need very good ones (huge ones too!), I have no idea who makes them. The chassis would be another mayor challenge. To summarize - the project seems to me risky (being generous here) for a person who's only built a tube amp kit. With time and help maybe you could do it.

PP triode with no global feedback doesn't sound like SE. Thank God.

Last edited by Cassiel; 18th May 2012 at 12:27 PM.
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Old 18th May 2012, 10:30 PM   #29
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petiert can help him with the output traffo....
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Old 26th June 2012, 08:03 AM   #30
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Quote:
Originally Posted by Tony View Post
i've done 8 KT88 trioded per channel: this baby eats 450watts idling:


Click the image to open in full size.
Do you have an schematic to have a look at?

Thank you,
Best regards
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