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General Discussion / Website maintenance Monday night
« Last post by Doc B. on Yesterday at 03:07:30 PM »The Bottlehead website will be down for maintenance Monday evening, May 27th.
Recent Posts
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General Discussion / Re: Transformers vs OTL
« Last post by Paul Birkeland on Yesterday at 11:31:03 AM »Is this for speaker amps or headphone amps?
OTL speaker amps tend to be a bit of a sticky topic on a lot of tube DIY forums. There are not a whole ton of tubes that are all that happy passing the kinds of currents you need to drive a loudspeaker, so you end up needing a ton of valves to get the job done. It's also tricky to maintain control of the current each valve draws without compromising the performance of the amp, and most often you'll see a generous lump of global feedback wrapped around these circuits to lower distortion and provide adequate damping. On the positive side of OTL amps, the parts cost is quite low and there aren't any complicated audio transformers to design and manufacture.
On the other side, SET amps typically use far more linear valves compared to those in OTL amps, far simpler circuits, usually a simpler power supply, but they require output transformers that are suitably made for audio performance, which isn't easy. With the output transformer, however, the same amp can be used on a wide variety of different speaker impedances by adjusting how the speaker connects to the secondary of the output transformer. To do this with an OTL amp isn't practical in any manner that I can think of.
If we are talking about headphone amps, typically OTL amps are a bang for the buck product that will synergize really well with higher impedance headphones that work well with an amplifier that isn't voltage limited. A good transformer coupled amplifier will typically outperform any OTL amplifier, but again this comes at the cost of highly specialized custom transformers that just aren't that easy to obtain.
OTL speaker amps tend to be a bit of a sticky topic on a lot of tube DIY forums. There are not a whole ton of tubes that are all that happy passing the kinds of currents you need to drive a loudspeaker, so you end up needing a ton of valves to get the job done. It's also tricky to maintain control of the current each valve draws without compromising the performance of the amp, and most often you'll see a generous lump of global feedback wrapped around these circuits to lower distortion and provide adequate damping. On the positive side of OTL amps, the parts cost is quite low and there aren't any complicated audio transformers to design and manufacture.
On the other side, SET amps typically use far more linear valves compared to those in OTL amps, far simpler circuits, usually a simpler power supply, but they require output transformers that are suitably made for audio performance, which isn't easy. With the output transformer, however, the same amp can be used on a wide variety of different speaker impedances by adjusting how the speaker connects to the secondary of the output transformer. To do this with an OTL amp isn't practical in any manner that I can think of.
If we are talking about headphone amps, typically OTL amps are a bang for the buck product that will synergize really well with higher impedance headphones that work well with an amplifier that isn't voltage limited. A good transformer coupled amplifier will typically outperform any OTL amplifier, but again this comes at the cost of highly specialized custom transformers that just aren't that easy to obtain.
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General Discussion / Transformers vs OTL
« Last post by Jimidick on Yesterday at 10:32:41 AM »I am new to the forum and have questions. I have looked at kits from Bottle head and Transcendent Sound. What will I hear as the difference between using transformers and OTL? Other pros and cons? Thanks for your input.
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Crack / Re: Low noise + wrong voltages
« Last post by Paul Birkeland on May 24, 2024, 10:36:04 AM »One side of that board is not well soldered.
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Crack / Re: Low noise + wrong voltages
« Last post by vermeil on May 24, 2024, 04:12:10 AM »By the front C4S board, do you mean the small green one?
Would this be correct?
Would this be correct?
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BeePre / Re: Resistance Check on 52
« Last post by Paul Birkeland on May 23, 2024, 01:54:26 PM »If the resistance readings are good, be sure to check the resistors going to the tube socket pins themselves.
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Crack / Re: 12au7 not glowing
« Last post by watonwak on May 23, 2024, 10:40:47 AM »Thanks Doc, it was the B7 end that had come off. It had snapped at the joint with not quite enough slack so had to replace the wire, but its all working great now!
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Crack / Re: 12au7 not glowing
« Last post by Doc B. on May 23, 2024, 09:44:46 AM »12AU7 heaters are not getting power. Check and maybe reflow the green wires connected at the A4/5 and A9 socket connections and also the other ends of those wires at B7 and B8.
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Crack / 12au7 not glowing [resolved]
« Last post by watonwak on May 23, 2024, 09:01:10 AM »hello,
i was doing some rework to my crack with speedball, tidying up joints to try and fix some intermittent noise, but now my 12au7 and its LED's no longer glow, and i am reading about 180v on 0A and 0B on the small board. Have i messed up something obvious? All other LED's light and so does the 6080. Thanks
Edit: I checked the LED's with my meters diode check and they do both glow
i was doing some rework to my crack with speedball, tidying up joints to try and fix some intermittent noise, but now my 12au7 and its LED's no longer glow, and i am reading about 180v on 0A and 0B on the small board. Have i messed up something obvious? All other LED's light and so does the 6080. Thanks
Edit: I checked the LED's with my meters diode check and they do both glow
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BeePre / Re: Resistance Check on 52
« Last post by Emoreigns on May 23, 2024, 07:00:05 AM »Good Morning Paul,
Am I just looking at the (2) 130 ohm resistors and the (1) 330 ohm resistor for each tube? Or is there somewhere else I need to verify too-
Because, After triple checking these 6 resistors ( 4 130 ohm and 2 330 ohm) I am positive the resistance readings across the resistors themselves, and the terminals they are soldered to are the same?
Perhaps I am just not looking at the right spot? Probably just another noob move out of me here-
Am I just looking at the (2) 130 ohm resistors and the (1) 330 ohm resistor for each tube? Or is there somewhere else I need to verify too-
Because, After triple checking these 6 resistors ( 4 130 ohm and 2 330 ohm) I am positive the resistance readings across the resistors themselves, and the terminals they are soldered to are the same?
Perhaps I am just not looking at the right spot? Probably just another noob move out of me here-