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Old 28th March 2012, 07:08 AM   #11
Stixx is offline Stixx  Germany
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Navyblue, you have PM.
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Old 29th March 2012, 01:38 PM   #12
rjm is offline rjm  Japan
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The central idea for these amps is that they be cheap. What this means in practice is salvage iron: if you are paying the going rate for new output and power transformers, as well as perhaps filter chokes, you'd be better served by a better circuit with a proper driver stage and higher power, better-sounding output tubes.

So, essentially, you usually end up designing the circuit around whatever iron you accumulate off ebay or wherever, and the tubes in your drawer. If it's for headphones rather than speakers, you have to pay a bit more attention to hum and noise. If it's for desktop speakers, pretty much anything goes.

The basic, fundamental problem is the output transformers: if they are small and cheap, there's no bass response and the sound is lo-fi. If they are large and expensive, you are wasting your time with crap tubes when you should be building a 2A3 DHSET.

By the way, the single stage design is a low-rent shortcut, not a "less-is-more" hi-fi thing. Driving the output stage directly from a 50k or 100k volume pot will work, just, but it is unlikely to sound very good. Volume dependent frequency response ... practically shouts "student dorm".
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Last edited by rjm; 29th March 2012 at 01:42 PM.
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Old 29th March 2012, 06:31 PM   #13
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I get the impression that SET amps are not known for their technical abilities, but rather for their coloured sound. Am I right to think that?

Say I am getting a custom transformer from say Electraprint, so you suggest that I should be looking at 2A3 tubes? Is there a schematic out there that you can point me in the direction of?

Thanks.
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Old 29th March 2012, 07:02 PM   #14
Stixx is offline Stixx  Germany
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Quote:
The central idea for these amps is that they be cheap. What this means in practice is salvage iron: if you are paying the going rate for new output and power transformers, as well as perhaps filter chokes, you'd be better served by a better circuit with a proper driver stage and higher power, better-sounding output tubes.

So, essentially, you usually end up designing the circuit around whatever iron you accumulate off ebay or wherever, and the tubes in your drawer. If it's for headphones rather than speakers, you have to pay a bit more attention to hum and noise. If it's for desktop speakers, pretty much anything goes.

The basic, fundamental problem is the output transformers: if they are small and cheap, there's no bass response and the sound is lo-fi. If they are large and expensive, you are wasting your time with crap tubes when you should be building a 2A3 DHSET.

By the way, the single stage design is a low-rent shortcut, not a "less-is-more" hi-fi thing. Driving the output stage directly from a 50k or 100k volume pot will work, just, but it is unlikely to sound very good. Volume dependent frequency response ... practically shouts "student dorm".
Are you trying to make a point with your biased ...err.. statements?
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Old 17th March 2014, 05:48 PM   #15
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by Navyblue View Post
I get the impression that SET amps are not known for their technical abilities, but rather for their coloured sound. Am I right to think that?
I believe SETs can be designed to be sound neutral sounding even if not of the lowest distortion.
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Last edited by Bigun; 17th March 2014 at 06:01 PM.
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Old 18th March 2014, 02:54 PM   #16
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Originally Posted by rjm View Post
By the way, the single stage design is a low-rent shortcut, not a "less-is-more" hi-fi thing. Driving the output stage directly from a 50k or 100k volume pot will work, just, but it is unlikely to sound very good. Volume dependent frequency response ... practically shouts "student dorm".
Maybe you can help me understand As the volume goes up and down the frequency response changes?

DHTROB made one of these with 5842 tube and says it sound amazingly good but from what your saying that should not be the case.
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Old 20th March 2014, 12:15 PM   #17
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I guess he was referring to Miller effect. Plate-to-gate capacitance appears magnified by voltage gain (and so does any voltage-dependent variation, if applicable).

One would have to consult the datasheet and do the math (RC lowpass). Maximum output impedance of a pot driven by a low-impedance source is Rpot/4.
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Old 16th April 2014, 08:48 PM   #18
jpak is offline jpak  United States
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Originally Posted by Stixx View Post
Dsavitsk's spud amps are well thought out... though I haven't built them I would recommend them.

For the Torpedo you could check the HeadFi site... there's a few discussions and an official build thread.

Then I have built quite a few headphone amps myself... the last one being a spud amp based on the german C3G transformer coupled and fed by a Salas shunt reg. See schematic attached --> it has been refined since and sure sounds gorgeous.
Which 10k:300 OPT did you use, I take it was custom order?
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Old 18th April 2014, 03:56 PM   #19
Stixx is offline Stixx  Germany
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Jpak,

I wound up using Lundahl LL1689... there's a pic somewhere in the Gallery.
Or check out my sig
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Old 22nd April 2014, 07:51 PM   #20
jpak is offline jpak  United States
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Originally Posted by Stixx View Post
Jpak,

I wound up using Lundahl LL1689... there's a pic somewhere in the Gallery.
Or check out my sig
Thanks for the info! I am a HD800 fan as well
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