Hi Rick,
Mine are made out of copper foil and are about 2cm shorter than the top of the st type tube, and fit tightly and then soldered along the entire seam. The foil is probably less than 0.7mm thick.. For grounding they just touch the chassis, and are just heavy enough to make a reliable contact, has worked for over a year now.
Even aluminum foil will work.
Mine are made out of copper foil and are about 2cm shorter than the top of the st type tube, and fit tightly and then soldered along the entire seam. The foil is probably less than 0.7mm thick.. For grounding they just touch the chassis, and are just heavy enough to make a reliable contact, has worked for over a year now.
Even aluminum foil will work.
OT: 845 Amp question
Well I was working on one, but I have shelved the idea for the time being as I'm not sure that it will meet my performance criteria. I have a number of friends who designed and built 211/845 amplifiers, only to find to their chagrin that 2A3/50/300B based se amplifiers sounded considerably better.
I started with 45's and have designed and built lots of amps using 2A3, and 300B so now I have very cold feet.. It's a huge investment and in light of these findings and having heard one of the 845 amps in question I unfortunately have to concur. I'm not likely to buck the trend, these particular amp designers are extremely talented.
My next amp will most likely be 50 based.. (Maybe TJ)
Well I was working on one, but I have shelved the idea for the time being as I'm not sure that it will meet my performance criteria. I have a number of friends who designed and built 211/845 amplifiers, only to find to their chagrin that 2A3/50/300B based se amplifiers sounded considerably better.
I started with 45's and have designed and built lots of amps using 2A3, and 300B so now I have very cold feet.. It's a huge investment and in light of these findings and having heard one of the 845 amps in question I unfortunately have to concur. I'm not likely to buck the trend, these particular amp designers are extremely talented.
My next amp will most likely be 50 based.. (Maybe TJ)
Hi Kevin OT re 845
Have you or your friends read the postings by Grover Gardner posting as "Groverg" at www.audioasylum.com/forums/tubediy/bbs.html or on the Joe List archives?
Grover who has built about twenty 845 amps believes that while it’s harder to get an 845 right, it’s possible to get it “better”.
Cheers
Have you or your friends read the postings by Grover Gardner posting as "Groverg" at www.audioasylum.com/forums/tubediy/bbs.html or on the Joe List archives?
Grover who has built about twenty 845 amps believes that while it’s harder to get an 845 right, it’s possible to get it “better”.
Cheers
I have built 26 pre (Kevin helped me a lot) with Salas HV supply feeding EP 200H plate chokes and SMPS+simple 317 regulator for filament. This hum free nice sounding pre is now settle along with my other audio gear.
http://www.diyaudio.com/forums/tubes-valves/151421-26-pre-amp-36.html#post2137037
BTW, why the driver tubes? Doen't it add color to the perfect 26 sound?
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Coolzero,
Your schematic is quite simple and I thought I'd go for it, but can you tell me why there is a 0.15 at the signal path ?? Does it affects the sound ??
Thanks
Albert
Hi!
The 0,15uF cap in this schematic is needed to block the DC from the bias battery from the pot and the input. If you want to avoid the cap you need to go for cathode bias.
Also note this design has a very high output impedance of 7k Ohm. Way too high for a preamp IMHO. It will react sonically to the load and cables on it's outputs
Best regards
Thomas
The 0,15uF cap in this schematic is needed to block the DC from the bias battery from the pot and the input. If you want to avoid the cap you need to go for cathode bias.
Also note this design has a very high output impedance of 7k Ohm. Way too high for a preamp IMHO. It will react sonically to the load and cables on it's outputs
Best regards
Thomas
Thomas,
What if I want to keep the battery bias. How could I lower the output impedance ??
Albert
I've just put together a 26 preamp with filament bias which uses the LL1660/5mA as outputs in 1:1. I don't need a step-down because I have short leads to the tube amp. Plus I need the amplification factor!
This sounds really good. The inductance is enough to suit the 26 nicely. The LL1660/10mA is 130H in 1:1 which is somewhat less than the 5mA one. Maybe you are using it in step-down though.
Andy
Hi Andy,
I understand that you need that gain and have your reasons not to use the step down. But I'd encourage you to wire it 4.5:1 just as a test. Even if you cannot listen at the normal levels this will give you an indication how much better this will sound. Maybe you will like it. If so try to get the gain back somewhere else. This is a mod which takes minutes, is quickly reversed and will tell you a lot!
Best regards
Thomas
I understand that you need that gain and have your reasons not to use the step down. But I'd encourage you to wire it 4.5:1 just as a test. Even if you cannot listen at the normal levels this will give you an indication how much better this will sound. Maybe you will like it. If so try to get the gain back somewhere else. This is a mod which takes minutes, is quickly reversed and will tell you a lot!
Best regards
Thomas
Thomas,
Thanks so much for your advice and encouragement. What happen is I had my 26 built some year ago and since it hummed so loud that I had to put it aside without touch it. I finished my 26 pre with VT-52 design and you could see the attachment for the pics. Since I'm old and don't know electronics too much but very much love listening to music. I don't want to break my bank for the system and therefore I start my diy journey. I really would love to make a good system for myself and I again started some years ago to copy directly from those designs that I could found at the forum.
Back to the topic. My power amp is with 100K input impedance, all my interconnects are within 1 meter in length and I only have CD as source.
Please do check the attachment for the schematic which is partly copy from Kevin's design with battery bias. Tell me if it'd work or anything I could do it better.
Attachments
Hi!
The schematic does not show a connection from the 26 filament to ground. One side needs to be grounded. I'm not familiar with the Salas reg. I assume it is not just a CCS as indicated in the schematic. ust a CCS would not work. If it has low output impedance the reg should work, but then there must be some reference to ground from the reg as well.
If the above is done it should work. It could be done much better IMHO, but that would require some expense. I'd get it to work like this and if you want to modifiy it afterwards, you can ask again.
Thomas
The schematic does not show a connection from the 26 filament to ground. One side needs to be grounded. I'm not familiar with the Salas reg. I assume it is not just a CCS as indicated in the schematic. ust a CCS would not work. If it has low output impedance the reg should work, but then there must be some reference to ground from the reg as well.
If the above is done it should work. It could be done much better IMHO, but that would require some expense. I'd get it to work like this and if you want to modifiy it afterwards, you can ask again.
Thomas
Thomas,
Please check attached for Sala's reg. I'd try to show Rod's heater supply later.
Thanks
Albert
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