adamus
500+ Head-Fier
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- Feb 29, 2008
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Looking through so many valve amp threads there are so many that are OTL (output tranformerless).
Do we think its just economics? Good 470uf low esr electrolytics are about £7 each. Reasonable performing transfomers can be had for £20, really good transformers are ~£100 each.
I have three amps on my desk
1) OTL (6n1p@ 170 10ma if interested, 470uf output caps bypassed), with reasonably low output impedance, so is fine down to 80ohms heaphones.
2) Parafeed with cheap edcor transformers, film caps as parafeed cap. (6e6p-dr @35ma 180v)
3) single ended, £££transformers. (6e6p-dr @ 30ma 180v)
I havent done distortion measurements, but have checked basic waveform, no issues, no hum, no oscillation. On all i set gain set equally for a given load (as in my opinion more gain always tricks the brain to be 'better').
Best? probably 2. maybe 3. maybe 1!
2 sounds the most accurate. 3 sounds slightly more fluid (it certainly has a softer powersupply - less well regulated), 1 is what most would describe as 'tubey' i.e. warm highs, slightly bloomy mids and the least accurate bass. 1 is great for long listening whilst working as it creates such a mellow sound so zero fatigue, but i wouldnt describe it as a good amp, its a coloured amp that has a purpose.
The BIG benefit of 2 & 3 is they drive any headphones as you can match impendance, hell they will drive efficient speaks if needs.
The OTL will drive lower impendance with a big dose of Negative feedback, but does it negatively impact the sound...? lots of folk say so (I am not so sure - again think its probably more the big reduction in gain that confuses people).
So why do we see OTLs dominate the commercial offering?
Do we think its just economics? Good 470uf low esr electrolytics are about £7 each. Reasonable performing transfomers can be had for £20, really good transformers are ~£100 each.
I have three amps on my desk
1) OTL (6n1p@ 170 10ma if interested, 470uf output caps bypassed), with reasonably low output impedance, so is fine down to 80ohms heaphones.
2) Parafeed with cheap edcor transformers, film caps as parafeed cap. (6e6p-dr @35ma 180v)
3) single ended, £££transformers. (6e6p-dr @ 30ma 180v)
I havent done distortion measurements, but have checked basic waveform, no issues, no hum, no oscillation. On all i set gain set equally for a given load (as in my opinion more gain always tricks the brain to be 'better').
Best? probably 2. maybe 3. maybe 1!
2 sounds the most accurate. 3 sounds slightly more fluid (it certainly has a softer powersupply - less well regulated), 1 is what most would describe as 'tubey' i.e. warm highs, slightly bloomy mids and the least accurate bass. 1 is great for long listening whilst working as it creates such a mellow sound so zero fatigue, but i wouldnt describe it as a good amp, its a coloured amp that has a purpose.
The BIG benefit of 2 & 3 is they drive any headphones as you can match impendance, hell they will drive efficient speaks if needs.
The OTL will drive lower impendance with a big dose of Negative feedback, but does it negatively impact the sound...? lots of folk say so (I am not so sure - again think its probably more the big reduction in gain that confuses people).
So why do we see OTLs dominate the commercial offering?
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