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OTL amps for guitar duty
OTL amps for guitar duty
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Old 4th February 2017, 05:43 PM   #1
multi-volti is offline multi-volti  United States
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Default OTL amps for guitar duty

I didn't want to read all 73 pages on this amp, but skimming through, I got the impression some people found answers.

If anyone hasn't mentioned it, there are capacitor component designators repeated in the power supply schematic...that bothered me less than the output tube pin numbering error (based on assumptions about where pin 1 actually is).

I am apprehensive about the direct coupling and DC protection, but apparently Tim Mellow has one in his home and hasn't consumed any voice coils.

That fear remaining, I was thinking about a guitar amp with less costly speakers. I noted the availability of greater power output with higher impedance loads, but finding a 32-50 ohm voice coil seems like a big waste of time. 4 x 8 ohm speakers in series? Ugh? Would sound better than a bank of resistors, I guess.

I already have the tubes, sockets and applicable power transformers and it's not a terribly complicated amp...so it still has my interest.

OTOH, a mid grade Edcor OT for 6C33C-B isn't a lot of money. Or build both. Lack of time seems to be a bigger problem.
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Old 5th February 2017, 05:22 AM   #2
AquaTarkus is offline AquaTarkus  Canada
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Quote:
Originally Posted by multi-volti View Post
, I was thinking about a guitar amp with less costly speakers.
I doubt that this type of amp would serve well as a guitar amp, in common with most hifi amps. Guitar amps are made to add colour and warmth to the natural sound of the guitar.

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Old 5th February 2017, 09:46 AM   #3
goddlediddles is offline goddlediddles  Ireland
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OTL amps for guitar duty
Quote:
Originally Posted by multi-volti View Post
I didn't want to read all 73 pages on this amp, but skimming through, I got the impression some people found answers.

If anyone hasn't mentioned it, there are capacitor component designators repeated in the power supply schematic...that bothered me less than the output tube pin numbering error (based on assumptions about where pin 1 actually is).

I am apprehensive about the direct coupling and DC protection, but apparently Tim Mellow has one in his home and hasn't consumed any voice coils.

That fear remaining, I was thinking about a guitar amp with less costly speakers. I noted the availability of greater power output with higher impedance loads, but finding a 32-50 ohm voice coil seems like a big waste of time. 4 x 8 ohm speakers in series? Ugh? Would sound better than a bank of resistors, I guess.

I already have the tubes, sockets and applicable power transformers and it's not a terribly complicated amp...so it still has my interest.

OTOH, a mid grade Edcor OT for 6C33C-B isn't a lot of money. Or build both. Lack of time seems to be a bigger problem.
Nobody has reported speaker destruction when fed from this amp - YET.

OK, it's living dangerously but the sound from the amp is A1. If you accidentally knock one of the 6C33Cs out of its base, you get full HT across your speaker. It's a bit more difficult to build than you think; sourcing the right components was my biggest difficulty.

It would be be completely unsuitable for a guitar amp; it's really only for pure HI-Fi aficionados The sense of reward and achievement after building it is immense when you hear the end results. BTW, there is a previous thread on the same amp which is also very informative. Reading all posts on both threads is worth the effort - both inspiring and slightly daunting.
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Last edited by goddlediddles; 5th February 2017 at 09:49 AM.
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Old 6th February 2017, 04:19 PM   #4
atmasphere is offline atmasphere  United States
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If you plan a guitar amp, there are 32 ohm 10" drivers intended for SVTs. !6 ohm drivers are easy to find.

I've been running OTLs for about 40 years and voice coil protection does not seem to be a serious issue. I think the old Futtermans could go into oscillation and fry tweeters and the like.
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Old 6th February 2017, 06:16 PM   #5
AquaTarkus is offline AquaTarkus  Canada
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Most guitar amp designers and builders will argue that the OT is an essential part of the tone. So unless we're talking of an amplifier for acoustic guitar, there's little point to using OTL technology.

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Old 6th February 2017, 07:09 PM   #6
atmasphere is offline atmasphere  United States
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I get that; however I've built a number of OTL guitar amps and found that was not the case.
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Old 6th February 2017, 08:02 PM   #7
AquaTarkus is offline AquaTarkus  Canada
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Are there any clips online that you could share?

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Old 6th February 2017, 09:15 PM   #8
atmasphere is offline atmasphere  United States
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Not yet- that seems like a good idea though!
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Old 7th February 2017, 01:00 AM   #9
multi-volti is offline multi-volti  United States
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Thanks Atma, Aqua & Go-Di...

I'm not thinking classic hardcore overdrive Strat/LesPaul amp practices...

more like archtop...not entirely clean, but more clean that not.

I see plenty of jazz guys using solid state class A amps like the German AER amps.

I'm just trying to make an effort to build something with my hoarded oddball items that sort of aligns with my oddball interests...of the moment...

I joke that if I ever finish a project, a piece of my soul dies...if I still have it...I might have traded it for a box of capacitors...
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Old 7th February 2017, 01:57 AM   #10
TonyTecson is offline TonyTecson  Philippines
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OTL amps for guitar duty
Quote:
Originally Posted by AquaTarkus View Post
Most guitar amp designers and builders will argue that the OT is an essential part of the tone. So unless we're talking of an amplifier for acoustic guitar, there's little point to using OTL technology.

Sent from my phone with Tapatalk. Please excuse any typpos.

yes, and power supply sag also, gives guitar amp its distinct sonic signature,
kit if crazy things these guitar heads do...
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