Audiomat CD2 OTL can be used in summer season just switch on the rear air fan.
Sure run very hot , and cost of 1kWh of energy is high.
Was pure class A , pure transformer less ( no output air coils or such )
huge psu transformers, build with hi quality industrial components no compromise all around.
ZOTL new generation compare to old shool Audiomat oh yeah can be interesting! Thanks and greetings
Sure run very hot , and cost of 1kWh of energy is high.
Was pure class A , pure transformer less ( no output air coils or such )
huge psu transformers, build with hi quality industrial components no compromise all around.
ZOTL new generation compare to old shool Audiomat oh yeah can be interesting! Thanks and greetings
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Amp for 32 ohm headphones based on DHTRob's 5842 amp from 2002. I tweaked the power supply and used no silicone. Tube complement is all-Raytheon NOS JAN 5842s and EZ81 rectifier. I was going to paint it a modern orange but for various reasons it ended up looking more industrial than I'd envisioned. Then I stumbled upon some green hammertone paint and ended up using that. So now it looks like vintage shop equipment (or a 1930s cinema amp). It sounds great. Finally able to listen to more music at night with computers off.
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Heavily modified Klipsch LaScala speakers. Different horn (Altec 511b) different driver (Selenium D250X) with baby cheeks horn and Eminence driver. Only part of Klipsch used is the bass bin. Biggest gain is better sound stage.
I really like the GU-50 tube when used as a strapped triode. Bass like a SS amp with mids as a true triode tube. The design is based on a Chinese amplifier being sold on Ebay. I bought the kit last year for something like $250 shipped and I liked the way it sound so much I decided to build another one with quality iron and better parts. I used carbon film resistors everywhere but the GU-50 cathode bias resistor which is 5 watts. Hammond PS trans with Edcor OPT's. Nothing exotic or terrible expensive. If anyone is interested I can PM schematic. The schematic calls for some feedback but I eliminated it on this build. Looks better using Arta without feedback.
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Here is the schematic of my build. I used 6H8C input, GU-50 output, and 5U4GB rectifier. I used the Hammond 276X PS trans with a Hammond 12.6V trans for the GU-50 filaments. Triadmagnetics -C-14X choke with Edcor GXSE10-3.5K OPT's. Carbon film resistors and I eliminated the feedback network. Best sound and better distortion analyzer shot without feedback. I have never used any feedback on any of my SET builds. I have built 10 or more of them. All the others have been built on bud box. I decided to try and make this one more pretty. I reduced the plate voltage somewhat with the big white resistor 250 ohm 10 watt. With my wall voltage being somewhat high it needed reducing. Still a touch high but no red spots on plates so I am going with just 250 ohms.
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Some years ago I purchased a Bottlehead "Quickie" linestage. This linestage makes use of a 3S4 tube, which is a directly heated pentode. The entire amp is battery powered. It uses four 9v batteries for 36v of B+ and two 1.5v (D) batteries for the filaments. Both filament and B+ last about 200 hours using standard alkaline cells. I opted for a CCS load for the plate, a standard option. The tubes don't even get warm to the touch, a nice quality on these hot days!
This amp can sound quite good (IMHO) but paired with higher power solid state amps can be very microphonic. The issue is partly related to gain.
For a while I'd considered trying a cathode follower version of this amp to see if that would change/help things. With some help from the Bottlehead crew (they are very generous helping users try new things), I finally got a working version wired up over the holiday weekend. I used a piece of galvanized tin for the top plate and a simple box for a standard style of build. Nothing fancy but this was really just a test. Except I'm likely to live with it for a while before trying to improve the aesthetics.
So here it is, in it's junk bin glory. I basically used parts I had lying around, including a few pairs of 3S4 tubes. In this version, I send 36v from the 9v stack to the plates. The cathode/filament (there are two connections allowing 1.5v parallel or 3v series) connects to the heater batteries ("D" cells, one per channel) and below them is a 3.9k resistor to the bottom of the 9v stack. The inputs and outputs are grounded at the top of the first 9v battery giving the cathode an effective -9v supply. This provides 2mA through the tubes (and a 2v grid bias I think).
This is a very nice sounding linestage and the microphonics are nearly gone. No ringing or humming when I reach for the volume knob, I can tap the tubes and only get a very short and quiet ring. The sound is quite articulate/fast/clear and it is basically very musical to my ears. With a LM3886 "chip amp" I built for hot weather use, it is remarkably pleasant. I think I'll be experimenting with it more.
Anyway, it's been a fun little aside. PS - the green topped amp is the original Quickie.
This amp can sound quite good (IMHO) but paired with higher power solid state amps can be very microphonic. The issue is partly related to gain.
For a while I'd considered trying a cathode follower version of this amp to see if that would change/help things. With some help from the Bottlehead crew (they are very generous helping users try new things), I finally got a working version wired up over the holiday weekend. I used a piece of galvanized tin for the top plate and a simple box for a standard style of build. Nothing fancy but this was really just a test. Except I'm likely to live with it for a while before trying to improve the aesthetics.
So here it is, in it's junk bin glory. I basically used parts I had lying around, including a few pairs of 3S4 tubes. In this version, I send 36v from the 9v stack to the plates. The cathode/filament (there are two connections allowing 1.5v parallel or 3v series) connects to the heater batteries ("D" cells, one per channel) and below them is a 3.9k resistor to the bottom of the 9v stack. The inputs and outputs are grounded at the top of the first 9v battery giving the cathode an effective -9v supply. This provides 2mA through the tubes (and a 2v grid bias I think).
This is a very nice sounding linestage and the microphonics are nearly gone. No ringing or humming when I reach for the volume knob, I can tap the tubes and only get a very short and quiet ring. The sound is quite articulate/fast/clear and it is basically very musical to my ears. With a LM3886 "chip amp" I built for hot weather use, it is remarkably pleasant. I think I'll be experimenting with it more.
Anyway, it's been a fun little aside. PS - the green topped amp is the original Quickie.
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I've had the Aikido Rev. A noval board for ages and I had even bought tubes for it but then forgot all about it. One day I was going through my project box and the board looked at me with such yearning sockets I had to do something about it.
So this is what I did about it. I don't know how well my attempt of recreating the cheesy 60's sci-fi style comes across, but that was the initial idea. Although I think I ended up with more Maxwell Smart than Captain Kirk, but that's OK. Never was a big Star Trek fan anyway. Most of the materials for the enclosure came from the scrapyard for next to nothing and the transformers are repurposed from old equipment as well.
The amp doubles as a line stage buffer and a headphone amp with 6CG7s, 6H30s and a GZ34+UF4007 hybrid rectifier. I'm still waiting for some PIO coupling caps to arrive in the mail and once they do and I get all the electronics done I'll post a picture of the guts. The front switches control the C1 and C2 coupling caps and the line out and headphone outputs. At the moment it's driving my LM3886 gainclone. Sounds fantastic BTW.
So this is what I did about it. I don't know how well my attempt of recreating the cheesy 60's sci-fi style comes across, but that was the initial idea. Although I think I ended up with more Maxwell Smart than Captain Kirk, but that's OK. Never was a big Star Trek fan anyway. Most of the materials for the enclosure came from the scrapyard for next to nothing and the transformers are repurposed from old equipment as well.
The amp doubles as a line stage buffer and a headphone amp with 6CG7s, 6H30s and a GZ34+UF4007 hybrid rectifier. I'm still waiting for some PIO coupling caps to arrive in the mail and once they do and I get all the electronics done I'll post a picture of the guts. The front switches control the C1 and C2 coupling caps and the line out and headphone outputs. At the moment it's driving my LM3886 gainclone. Sounds fantastic BTW.
