• 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.

One more 4P1L SE

signal source
dac pcm63p NOS
round wire potentiometer 25 ohm.for i / v converter and volume control
PC900 triode with plate choke
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AZ1 power supply channels individualized rl
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I am a bit glad speakers came up, for as much info on SET amps there is very little info on this site for modest high efficiency speakers, what are people without cad assisted machines doing for speakers. Are something like econo waveguides a good route to take for and amp this small powered. I have a pair of BR Fostex 127E but they just don't have any bass, I don't know where to look for info on modest budget horn setups.
 
For those interested in simulating their designs with SPICE, I developed a slightly refined DHT composite model using my own set of curves. A model is available for PSE as well.
Difference is on KP parameter which drives linearity of the model. With Dmitry's model you get a slightly worse THD response when swinging the 4P1L to its limits.

4P1L triode SPICE model | Bartola Valves

Hope this helps
Ale
 
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Those resistors should give you around 15R at 36W. Close enough for jazz.

If you are using glow tubes, it's useful to read the instructions for using them.
http://www.mif.pg.gda.pl/homepages/frank/sheets/141/g/GL874.pdf

You will see that for the octal glow tubes they need 22.5mA and the 7 pin ones need 17.5v. Subtract the minimum current from the maximum current and divide by two. Then add that to the minimum current. So for 0D3 max is 40mA, min is 5mA. Difference = 35mA. Half of that is 17.5V. Add that to the minimum 5v and you have 22.5v. For the 7 pins the max voltage is 30v, so current you need is 17.5mA. That is true of all glow tubes of these types.

So what you then do is add the current through the glow tube to the current through the tube(s) you are using. For 2 x 4P1L at 36mA, add 22.5v and you set the DN2540 for 58.5mA.
 
It's difficult to say if I prefer 4P1L or 26, because my amp is 4P1L into PSE 4P1L. Three stages of 4P1L are too much, so I'm using a 26 preamp. I'm going to try the 10Y next - I made a 10Y preamp before and preferred 26, but the 10Y wasn't optimised.

For a 4P1L preamp you need to do something about microphonics. Here's my latest idea using 1.5" plumbing parts. The brass parts don't touch the top plate - the rubber washers come in between, top and bottom. The tube socket is held between the two screwed pipes. I haven't tried it yet - should work! It's pretty heavy.....

Andy
 

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Yes, there will be transformers for parafeed drive. Let me test them first. I started a headphone 6W amp project about an year ago, then when potential partner became inpatient the project had been canceled, then the plant I contacted before come with some solution, so may be I will re-open the project if transformers are really as nice as they claim.

Do you have news?
 
It's difficult to say if I prefer 4P1L or 26, because my amp is 4P1L into PSE 4P1L. Three stages of 4P1L are too much, so I'm using a 26 preamp. I'm going to try the 10Y next - I made a 10Y preamp before and preferred 26, but the 10Y wasn't optimised.

For a 4P1L preamp you need to do something about microphonics. Here's my latest idea using 1.5" plumbing parts. The brass parts don't touch the top plate - the rubber washers come in between, top and bottom. The tube socket is held between the two screwed pipes. I haven't tried it yet - should work! It's pretty heavy.....

Andy

Hi Andy,

I am leaning towards the 4P1L-IS-4P1L-IS concept myself to drive a 300B.

I guess the first tube is the most problematic considering microphonics. Is it the vibrations passed on via the case or air vibrations which are the most problematic?

What is your latest anti microphonics solution?

Thanks,
Peter