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OTL amps for guitar duty
OTL amps for guitar duty
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Old 15th February 2019, 05:03 PM   #161
atmasphere is offline atmasphere  United States
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Old 15th February 2019, 10:04 PM   #162
efeemeka is offline efeemeka
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Hummm , i see one piece of sarcastic position here, or is the google translate?, or not undestand to me very goog by one moment?
I am spanish, an is dificult, for my the perfect expresión, I say reference to this is more sensitive to tone instrument, an not enmascarate nothing....

Nothing relationship whit the magic of cable, or the light of the cosmos, or blue pitufs.

Bad boys.
 
Old 16th February 2019, 11:14 AM   #163
45 is offline 45  Italy
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Originally Posted by atmasphere View Post
We've built a lot of guitar amps in our shop. Several of my employees build guitar amps which they play in their bands. None have come anywhere near the transparency of our OTL guitar amp; its much easier to hear the difference between a really good pickup and a cheap one, as well as the character of the guitar cable itself.
That's your experience.My experience is that most OPT's used in guitar amps are bad, including those from notorious firms.... I guess the one you used was no exception. For me OTL's have more troubles than advantages.

P.S.
I am actually assuming that one is sure about all the other things because often people attribute things to the wrong cause. The output transformer is often the scapegoat for other troubles that people are unable to spot. 99% of users of OTP's do not really know how it works and so it's easy to make up their mind about the "transparency" tale. That's just snake oil theory. a proper transformer can more transparent than any other electronic component. In the case of guitar amp where the bandwidth is even narrower that is absolutely true.
Personal beliefs, including generic comments about the sound, with no objective proof repeated over and over at some point become the truth. Real thing is different.
 
Old 18th February 2019, 10:21 PM   #164
atmasphere is offline atmasphere  United States
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Transparency and OTLs are two things that are often found together. IOW OTLs have been known for being really transparent for decades so this is nothing new.

I agree that a good transformer properly set up is quite transparent, but its also been my experience (over 4 decades now) that any transformer coupled amp we could get our hands on (and over the decades, that's been hundreds) just isn't going to be as transparent, and that includes amps that overall cost quite a bit more.

In that latter regard, one reason to go OTL is its less expensive. Unless you are going low power, output tubes tend to cost less than output transformers of the same power.

My advice is 'try it'. I find most of the push back I get comes from people who haven't.
 
Old 19th February 2019, 11:43 PM   #165
45 is offline 45  Italy
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Originally Posted by atmasphere View Post
Transparency and OTLs are two things that are often found together. IOW OTLs have been known for being really transparent for decades so this is nothing new.
In my experience they are only transparent on the bench driving a resistor. Not so transparent when driving real loudspeakers. They are actually quite fussy when it comes down to mate them with loudspeakers. Proper solid state amps are better for me if no transformer.

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Originally Posted by atmasphere View Post
I agree that a good transformer properly set up is quite transparent, but its also been my experience (over 4 decades now) that any transformer coupled amp we could get our hands on (and over the decades, that's been hundreds) just isn't going to be as transparent, and that includes amps that overall cost quite a bit more.
Be assured that if the OTL made a better guitar amp it would be at least a common solution among top of the range custom amps. Instead it isn't.

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In that latter regard, one reason to go OTL is its less expensive. Unless you are going low power, output tubes tend to cost less than output transformers of the same power.
Less expensive? Are you joking? I can do a 10W class A amplifier with 3 valves 1xECC83 and 2xPCL86, high quality capacitors and high quality transformers. The amp has two independent channels, one clean and one high gain with individual tone controls, presence switch. Only the first 1/2 ECC83 and output stage is in common. The clean channel outputs 10W super clean and 12W with some distortion (mostly 3rd and 2nd harmonics which results in a very light warm crunch when playing).

The output transformer is 16K plate-to-plate (a long story....) and weights less than 1Kg. Total parts cost is about 70 euros + 90 euros for the Eminence Legend 1028K + 30 euros for the reverb. If someone wants to buy it he would have to pay more because I have done the transformer myself however this would cost about 50 euros.

Can you make a 10W class A OTL amp for about 100 euros (excluding the loudspeaker driver and the reverb tank)?
I really doubt it.


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Originally Posted by atmasphere View Post
My advice is 'try it'. I find most of the push back I get comes from people who haven't.
I haven't tried for a guitar amp because I have tried for HiFi. Not good enough for me. Very fussy and thus anything but transparent in most cases.
For a guitar amp it should be easier however the sound of guitar amp is heavily dependent on the guitar, tone controls, effects of various types, speaker, gain stage that talking about the transparency of the output stage is like talking about everything and nothing at the same time.....

Last edited by 45; 19th February 2019 at 11:49 PM.
 
Old 19th February 2019, 11:53 PM   #166
Printer2 is offline Printer2  Canada
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Can you make a 10W class A OTL amp for about 100 euros (excluding the loudspeaker driver and the reverb tank)? I really doubt it.
That almost sounds like a Challenge. Woohoo!
 
Old 20th February 2019, 01:36 AM   #167
Tubelab_com is online now Tubelab_com  United States
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That almost sounds like a Challenge.
Isn't this how the HBAC started?

Let's see, 100 Euros is $114 USD as of 5 minutes ago......

Unfortunately those 6 inch Eminence guitar speakers that I have are 4 ohms.....

So assuming a 32 ohm load, and a 10 watt class A OTL, I'm guessing 4 X $3 output tubes, another 4 X $3 small signal tubes, a $35 power transformer, leaving about $55 USD for the rest of the parts......10 watt OTL amp, probably. Pretty case and fancy knobs, probably not.
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Old 20th February 2019, 02:26 AM   #168
Printer2 is offline Printer2  Canada
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Yeah but, any sand allowed?
 
Old 20th February 2019, 02:45 AM   #169
Tubelab_com is online now Tubelab_com  United States
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I don't know, I didn't start this one....I would assume SS rectifiers are OK. Mosfets? I'll use them if it is the right thing for the circuit.

The more I think about this the crazier it seems. I think I can do a 10 watt class A OTL. I figure that it will burn about 150 watts to make 10. The green police will have my number from the heat signature of 70 watts worth of tube heaters.

I have been working on an equally insane project, a music synthesizer built with vacuum tubes. Which is crazier, a tube synth, or an OTL guitar amp. Maybe I'll just build both and connect them together.
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Old 20th February 2019, 09:22 AM   #170
45 is offline 45  Italy
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Originally Posted by Tubelab_com View Post
Isn't this how the HBAC started?

Let's see, 100 Euros is $114 USD as of 5 minutes ago......

Unfortunately those 6 inch Eminence guitar speakers that I have are 4 ohms.....

So assuming a 32 ohm load, and a 10 watt class A OTL, I'm guessing 4 X $3 output tubes, another 4 X $3 small signal tubes, a $35 power transformer, leaving about $55 USD for the rest of the parts......10 watt OTL amp, probably. Pretty case and fancy knobs, probably not.
In the 100 euros/$114 also the metal chassis for the amp and the wood cabinet all put together and finished for a combo amp are included. Only the driver/drivers and the reverb tank are extra.
 

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