Broskie's Akikdo is an excellent preamp. SE qualities, dead quiet, no noise, low distortion, easy to build.
I use the 9-pin version with the 6GC7. Using the octal 6SN7 would also work very well for you. You could also try the 12AU7, just to hear what it sounds like.
PSU is very easy, hammond transformer, EZ81 rectifier tube, a couple caps and chokes.
Aikido output capacitor is easy to swap on the circuit board. Start out with something easy, like a Solen (cheap), and upgrade later to Mundorf or other.
http://www.tubecad.com/2006/08/blog0074.htm
IMHO, highest recommendation.
I use the 9-pin version with the 6GC7. Using the octal 6SN7 would also work very well for you. You could also try the 12AU7, just to hear what it sounds like.
PSU is very easy, hammond transformer, EZ81 rectifier tube, a couple caps and chokes.
Aikido output capacitor is easy to swap on the circuit board. Start out with something easy, like a Solen (cheap), and upgrade later to Mundorf or other.
http://www.tubecad.com/2006/08/blog0074.htm
IMHO, highest recommendation.
Re: Re: What preamp should I build?
Sort of... it's several transmitters with 1kW klystrons. They'll be decomissioned soon, It sure would be fun to make a 1kW plasma tweeter.
The tubes will be sold and the rest will probably go to scrap, it will be a shame Can you imagine the power of the SET amp the supplies could run?
Aikido and Poindexter's are looking like the leaders at the moment.
I'm wondering if the poor comments about the Aikido scome from poorly built examples, you tend to get that sort of thing with kits. I downloaded the instructions for it and there's a huge table of component values for various tubes.
I had another look at my Crossover circuit, it has +/- 15V rails so I should run the audio at a higher voltage for lower noise, then attenuate it back down to line level between it and the amplifiers.
so 10-15dB of gain will be fine. If anyone is interested I'm using active crossovers, with an aim to minimise the number of op-amps. these feed four channels of Tripath TA2024 class D amplification. I found a page about tube based active XOs last night so that might be an interesting one to tackle in future.
If I go with the Aikido are you saying I'd be better off with the 8 or 9 pin version? I do like their attenuator.
flg said:
Sort of... it's several transmitters with 1kW klystrons. They'll be decomissioned soon, It sure would be fun to make a 1kW plasma tweeter.
The tubes will be sold and the rest will probably go to scrap, it will be a shame Can you imagine the power of the SET amp the supplies could run?
Aikido and Poindexter's are looking like the leaders at the moment.
I'm wondering if the poor comments about the Aikido scome from poorly built examples, you tend to get that sort of thing with kits. I downloaded the instructions for it and there's a huge table of component values for various tubes.
I had another look at my Crossover circuit, it has +/- 15V rails so I should run the audio at a higher voltage for lower noise, then attenuate it back down to line level between it and the amplifiers.
so 10-15dB of gain will be fine. If anyone is interested I'm using active crossovers, with an aim to minimise the number of op-amps. these feed four channels of Tripath TA2024 class D amplification. I found a page about tube based active XOs last night so that might be an interesting one to tackle in future.
If I go with the Aikido are you saying I'd be better off with the 8 or 9 pin version? I do like their attenuator.
Another vote for the aikido. I built the 24V version. You can buy a complete regulated power supply off ebay for <$50. Uses 6GM8 tubes with the heaters wired in series, so it all runs off the 1 24V supply.
Its dead quiet, provides a useful amount of gain and sounds excellent. I'm in no position to judge amp designs, but can tell you my ears think the aikido is very very good.
24V aikido link
Fran
Its dead quiet, provides a useful amount of gain and sounds excellent. I'm in no position to judge amp designs, but can tell you my ears think the aikido is very very good.
24V aikido link
Fran
I like the 6GC7 (9-pin mini). As I understand tube history, the 6CG7 was an attempt to miniaturize the 6SN7 (8-pin octal). That's why the ratings are so similar.
Most hardcores will tell you (including Broskie) that the 6SN7 octal is superior to the 6CG7 9-pin version. If you are starting from scratch, go octal. There's no drawbacks in doing so.
Broskie's printed circuit boards have space for 2 output capacitors, so your preamp can have dual outputs. You can use different brand capacitors if you want to experiment with how capacitors sound.
The reason why there is a huge list of component values is the boards are very flexible and relatively insensitive to component values. For example, I could change the cathode resistors to anything from 330 Ohms to 800 Ohms with no real effect, other than it is arguable sonic differences would occur.
It's similar to the Pass Zen amplifiers, in which are rock-stable and you could get component values off by factors of 2 or 3 without suffering any ill side effects (some components can be off by factor of 10 or more).
I'm glad to hear good reports on the 24V configuration. I didn't trust it at first, and I'm still a little dubious.
The reason the Aikido is "dead quiet" is a self noise cancellation feature. You can get away with garbage power supplies, and the Aikido takes care of itself. It injects the PSU noise 180 out of phase, which cancels the PSU noise coming in. I use a PSU with capacitor-choke-capacitor configuration (photo attached), just because I hate noise that much.
I think the Aikido sounds great because it is a high input impedance, single-ended, low output impedance amplifier with no feedback. With the 6SN7 operating at 300VDC, it is operating on the flat spot of the triode's curve, giving very low distortion.
Most hardcores will tell you (including Broskie) that the 6SN7 octal is superior to the 6CG7 9-pin version. If you are starting from scratch, go octal. There's no drawbacks in doing so.
Broskie's printed circuit boards have space for 2 output capacitors, so your preamp can have dual outputs. You can use different brand capacitors if you want to experiment with how capacitors sound.
The reason why there is a huge list of component values is the boards are very flexible and relatively insensitive to component values. For example, I could change the cathode resistors to anything from 330 Ohms to 800 Ohms with no real effect, other than it is arguable sonic differences would occur.
It's similar to the Pass Zen amplifiers, in which are rock-stable and you could get component values off by factors of 2 or 3 without suffering any ill side effects (some components can be off by factor of 10 or more).
I'm glad to hear good reports on the 24V configuration. I didn't trust it at first, and I'm still a little dubious.
The reason the Aikido is "dead quiet" is a self noise cancellation feature. You can get away with garbage power supplies, and the Aikido takes care of itself. It injects the PSU noise 180 out of phase, which cancels the PSU noise coming in. I use a PSU with capacitor-choke-capacitor configuration (photo attached), just because I hate noise that much.
I think the Aikido sounds great because it is a high input impedance, single-ended, low output impedance amplifier with no feedback. With the 6SN7 operating at 300VDC, it is operating on the flat spot of the triode's curve, giving very low distortion.
Attachments
Hi Mike,
Some schematics from Vacuum State.
http://www.vacuumstate.com/schematics.htm
I like his stuff.
Cheers
Some schematics from Vacuum State.
http://www.vacuumstate.com/schematics.htm
I like his stuff.
Cheers
Wow, this tube forum moves fast.
I had a win today, a workmate gave me a bench supply, It's made by BWD, model 216a.
It has:
two independent 3 amp 6.3V filament supplies.
a 0-250Vdc 50mA supply.
a 0-400Vdc 400mA supply with adjustable current limit.
Unfortunately the 400V supply is faulty.
It has a few substantial dents in the housing but nothing appears loose or broken inside.
This looks like the perfect supply for me. If anyone has any suggestions for where I might find a circuit I would appreciate it.
I had a win today, a workmate gave me a bench supply, It's made by BWD, model 216a.
It has:
two independent 3 amp 6.3V filament supplies.
a 0-250Vdc 50mA supply.
a 0-400Vdc 400mA supply with adjustable current limit.
Unfortunately the 400V supply is faulty.
It has a few substantial dents in the housing but nothing appears loose or broken inside.
This looks like the perfect supply for me. If anyone has any suggestions for where I might find a circuit I would appreciate it.
I had a win today, a workmate gave me a bench supply, It's made by BWD, model 216a.
It has:
two independent 3 amp 6.3V filament supplies.
a 0-250Vdc 50mA supply.
a 0-400Vdc 400mA supply with adjustable current limit.>>>>
If the 6.3v supply is good rectified DC, I'd be tempted to try a pair of 6B4Gs using the 0-250v supply. Actually, I think 10Ys would run with a 6.3v supply, and that would be as good as you could get. One of the two filament supplies to each tube. You can find 10Y on ebay, or I have some.
It has:
two independent 3 amp 6.3V filament supplies.
a 0-250Vdc 50mA supply.
a 0-400Vdc 400mA supply with adjustable current limit.>>>>
If the 6.3v supply is good rectified DC, I'd be tempted to try a pair of 6B4Gs using the 0-250v supply. Actually, I think 10Ys would run with a 6.3v supply, and that would be as good as you could get. One of the two filament supplies to each tube. You can find 10Y on ebay, or I have some.
If you go the DHT gig, which I prefer, I have only been building for 2 years & conquered 26, ear laying against speaker quiet. ..But only by using outbourd PS located 3' away from 26's & filament supplies outbourd also, so 3 pieces just for my pre, not for everyone. One thing is I have not had is the microphonic issue's many have, I attribute this to the use of thick hard wood chassis only. I use oak in at least 1/2 but mostly 3/4. I do the same with my SET amps & same success with them in microphonics. Wood is GOOD....also 110ohm or whatever grid stopper seems key. Damper diodes are cheap & sound superiour to me for rect.. & also try glow tube shunt reg if you can, I also believe this sounds better & one more thing,,battery bias is pleasant & simple. I just used cap coupled jobbies with low part count albiet my power supply is nice & no lytics for me in PS, for non DHT 27 is killer in sonics but a beast to tame , much harder tha 26 IMO in the globe version I should say..but absolutely excellent sonics.. 90% of a 26 sonics but not the ultimate top end refinement & detail of 26.
Lotsa DHT & such to try that will add to the music experience. Passive TVC ways & such is something I hope to never have to do again...
Lotsa DHT & such to try that will add to the music experience. Passive TVC ways & such is something I hope to never have to do again...
Agree with all of the above - wood is good, and 4mm alu plate is also good - that's what helped me eliminate microphonics since it doesn't ring.
I also agree that if you want to make your first DHT pre, try an outboard filament and PSU first. If you put everything in one box and don't get it quite right it can drive you nuts.
I also agree that if you want to make your first DHT pre, try an outboard filament and PSU first. If you put everything in one box and don't get it quite right it can drive you nuts.
this grounded grid looks interesting.
http://www.transcendentsound.com/preampkit.htm
A simple no-brainer to get me started on these strange little light bulbs.
then again the T16 OTL looks good too. reviews are describing the qualities I like, extreme neutrality.
http://www.transcendentsound.com/preampkit.htm
A simple no-brainer to get me started on these strange little light bulbs.
then again the T16 OTL looks good too. reviews are describing the qualities I like, extreme neutrality.
Hi Mike,
Looks interesting and the price isn't bad at all!
I agree with the Neutrality quality but also enjoy a depth and nice soundstage and air restored. Probably opposite traits! LOL
Any idea on how it compares to the Bottlehead Foreplay III Extended? Or.... if there is a better choice for ~$1K US?
Thanks!
How are you enjoying your Summer "Down" there?
Regards//Keith
Looks interesting and the price isn't bad at all!
I agree with the Neutrality quality but also enjoy a depth and nice soundstage and air restored. Probably opposite traits! LOL
Any idea on how it compares to the Bottlehead Foreplay III Extended? Or.... if there is a better choice for ~$1K US?
Thanks!
How are you enjoying your Summer "Down" there?
Regards//Keith
No idea how it compares, A friend of mine built the transcendent Single Ended OTL and was impressed with the quality of the sound and the materials.
The transcendent kit is appealing because it's all there, I don't have to hunt about for hours to get all of the parts. If I find it's not for me it's professional looking so it would be easy to sell.
The weather?... I live at 20 degrees south in a desert. This is about the only time of year it rains, and only during cyclones/hurricanes.
Friday night I was called out for work and it was 30 degrees celsius, at 2am.
Humidity is low today so it's quite nice. I'm using the opportunity to get some things done outside.
The transcendent kit is appealing because it's all there, I don't have to hunt about for hours to get all of the parts. If I find it's not for me it's professional looking so it would be easy to sell.
The weather?... I live at 20 degrees south in a desert. This is about the only time of year it rains, and only during cyclones/hurricanes.
Friday night I was called out for work and it was 30 degrees celsius, at 2am.
Humidity is low today so it's quite nice. I'm using the opportunity to get some things done outside.
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