• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

#26 pre amp

Those Neutrik 8 way speakons are useful. I use the 4-way ones and 4 pin XLRs. I found the 8 way speakons a bit annoying to use - I don't like having to use allen keys and I have had the odd wire come loose on the cable connectors I have. I believe there are newer models with a solder alternative. Prices have gone up a lot - it's much cheaper to get used 4-pole ones on ebay or whatever.
 
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XLRs have enough voltage spec for filaments - they're rated 50v I believe, though were previously rated more. Smaller and cheaper than speakons. With Speakons, one theoretical problem is what they're designed for. The Powercons are mains AC connectors, so anyone unfamiliar with the equipment could plug the mains into the preamp. Speakons are just as bad - some unsuspecting person could connect the B+ from the PSU to a loudspeaker. I'm not thrilled with any of these choices. The XLRs are fine, and I tolerate using the Speakon 4 poles especially since they're rated 300v, but it's not a correct engineering choice.
 
You can't plug white Powercon to blue Powercon:D

Yes, I know, but they're designed for AC power. I'm just thinking of future times when our experiments may fall into other hands. Maybe I'm just being paranoid. The obvious thing is to put clear instructions on the chassis for what the connectors do. We don't do this because we know what is what, but others won't if they just find the stuff in a cupboard one day. I haven't even looked into ways of engraving specifications on plates that can be screwed onto a chassis - anybody into this kind of thing?
 
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Due to lack of mid-bass & bass using two 40uF ASC MKP in oil as AC mains filter I changed to BG, I use with ASC & BG L-C-L-C each C with BG is 200uF each L is 10H 100mA, improved but I guees still can be improved more, the question is: I use AZ1 but the after the AZ1 isn't direct to a cap so can I use 200uF as first cap after the choke? or I have to change to C-L-C-L-C and first cap FT3 0,1 or 0,47uF? can be that 26 need more capacitance to filter AC mains?

TIA
Felipe
 
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Just for fun attached pic with BG
 

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Due to lack of mid-bass & bass using two 40uF ASC MKP in oil as AC mains filter I changed to BG, I use with ASC & BG L-C-L-C each C with BG is 200uF each L is 10H 100mA, improved but I guees still can be improved more, the question is: I use AZ1 but the after the AZ1 isn't direct to a cap so can I use 200uF as first cap after the choke? or I have to change to C-L-C-L-C and first cap FT3 0,1 or 0,47uF? can be that 26 need more capacitance to filter AC mains?

TIA
Felipe

Hi Filipe, if it can be of any use, I use AZ11, with C-L-C-2xL-2xC, where first C is ASC premium (blue cover) 8uF, first L is lundahl 1638 10H, second C is ASC 40uF then splits in two lines with Hashimoto 30H chokes, into two last ASC 40uF capacitors. These lines then feeds 2 Salas HV2 shunts, one by chanel.

Sound is great and DEAD quite!

Hope I could help, good luck for your building.

Cheers.
 
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Thanks for let me know what are you using, AZ1 specs says 1st cap max 60uF I guess isn't my case because 1st component is a 10H choke.

My 26 is also dead quite can be that I have to look for in other directions like the Legato is only giving 1.5VRMS in place of 2VRMS & 26 only have a gain of 6 dBs but when used the two ASC 40uF I didn't have the sensation of weak of power, the sensation was weak of mid-bass & bass so a sound extremely analytic, clean, fast and direct.
 
The bad sound was the ST tubes, now I use globe tubes and sounds right:)

Hi Felipe,
ST are not any better than globe ones. You may have had a bad pair of ST valves. Some of them are prone to pick up hum, some aren't. You just need to select a good pair. I noticed in globe ones when I tested some with the curve tracer that electrodes may be slightly misaligned and the distortion levels are higher. If not in good shape, they won't sound good at all. On the flip side, a good pair of Sylvania o Silvertone ST ones sound marvelous.
It has been said before, but it's worth repeating. The globe ones tend to have higher H2 distortion and will sound naturally sweeter than the ST ones. It all depends. I sometimes put back my ST depending the music I'm listening to. It's a question of personal taste as well.
Ale
 
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Hi Ale,
I'm listening DSD128 & DSD64 native and sounds wonderful as never sounded my system, no coloration, very clean and clear, no hum is silent as a tob like with ST, only nice sound specially with classical music. No come back to ST till globes gone out, also I'm using Rod Colemans filament heaters so not easy change the tubes without adjust the filament voltage, speaking of heaters my system sounded better with starving filament 1,35VDC, also sounded better with BG in the mains filter than ASC MKP in oil, with BG magic, with MKP only big sound with no magic....
Felipe
 
hi , i'm on the way to building mine after the excellent 6AH4 line stage thomas mayer help me to build. i have already a LCLCLC external power supply and CCS VR reg CCS as plate load and some tentlabs filament reg.

my question is for the crosstalk : is it necessary with the CCS plate loading two separate B+ with separate CCS VR regulation ? :spin: