• 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.

Look for Single Tube scheme

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Wavebourn

Wavebourn

Member
Joined 2006
wavebourn.com
dsavitsk said:
EML-20A-20B-30A Data sheet. By Emission Labs.
Click to expand...

Have you seen their curves? :rolleyes:


Here are curves of 4P1L: less than 2K in triode mode, 10 mA/V

life6.gif
 
M

mik190

Member
Joined 2009
Hi everybody

Thank you for proposals. Some replies to all in one post :)

1. 6C45P - I found several schemes about it but in reality it was only 0.5-1W in single stage amplification that is not enough for me. Similar schemes are for 6J51P, 6J52P. The are good for preamlifier or amplifier for computer (in this case it might be done as a single tube). Will make look at your variants at weekend. SRPP might be a good idea (1.5W)

2. It is intersting idea from Wavebourn. At the moment I am finishing SE amplifier at 6S2S + interstage trans + 4P1L. Will make some posts about it later. But idea to use 4P1L as single stage is interesting.

3. Other ideas will lok at weekend and reply.

Thank you all.
 
artosalo

artosalo

Member
Joined 2010
The advantage of needing 3 voltsdrive for full power is that you won't over drive it with typical CD players.
Click to expand...

I do not see the low sensitivity as any advantage.
The danger of possible over drive by a high output CD-player is avoided with volume control ofcourse.

But if the music source happens to be a low output MP3-player with 0,7 V for example, then the amplifier with 3 V input sensitivity is quite useless.

So as we still discuss about single tube amplifier, the higher gm-tube is an advantage.
 
M

mik190

Member
Joined 2009
Jaime said:
The 4P1L is direct heating tube.:)
You need a 1:4 trans at the input in single stage 4P1L option.
Click to expand...

This weekend I launched my 6S2S+interstage trans+4P1L project. First impression is exellent and very detailed sound (better then my 300B based SE) but with low power 2W per channel. So one need horn speakers for it. But to go forward for single stage is a good idea. Will look for good input trasformer for it. For such minimalistic design qualiti of input transformer is very important.
 
R

rock4016

Member
Joined 2005
artosalo said:
I do not see the low sensitivity as any advantage.
The danger of possible over drive by a high output CD-player is avoided with volume control ofcourse.

But if the music source happens to be a low output MP3-player with 0,7 V for example, then the amplifier with 3 V input sensitivity is quite useless.

So as we still discuss about single tube amplifier, the higher gm-tube is an advantage.
Click to expand...

Your 6j52p suggestion is great until you look at the anode dissapation. It's a little light, not good for a SINGLE tube amp, as in the case of this discussion. You'd want something bigger like a 6C45pi with closer to 8w plates.
 
artosalo

artosalo

Member
Joined 2010
Your 6j52p suggestion is great until you look at the anode dissapation. It's a little light, not good for a SINGLE tube amp, as in the case of this discussion. You'd want something bigger like a 6C45pi with closer to 8w plates.
Click to expand...

I don't see your point. Please try to make me understand.

The Pa max. for 6S45P is 7,8 W and 10 W for 6J52P.
Actually I do not even know (so far) any better valve for single tube amplifier than 6J52P.

Two other good candidates are:
- E810F (Pa = 5 W, gm = 50 mA/V) and
- WE437A (Pa = 7,0 W, gm = 46 mA/V)

Compared to 6J52P ( Pa = 10 W, gm = 55 mA/V)

In my opinion, the optimal tube for a single tube amplifier is such that has as large gain as possible combined with as high anode dissipation as possible .
 
R

rock4016

Member
Joined 2005
The datasheet I saw on the 6j52p had 5w plates, guess my russian is not up to spec.

How about a tube George mentioned in the 20W single tube thread.

"The 6HV5A and relatives. Transconductance is 65000, Mu is 300, plate dissipation is 35 watts. The plate is big enough to eat a bit more than 35 watts. So. it's a done deal, right? Not so easy. The tube needs a bunch of voltage, and it's plate resistance is real high, so feedback is almost mandantory. I have experimented a bit with this tube and have yet to tame it. Good luck! "

Sounds like it would be an interesting canidate that would need more experimentation, but the possibility of over 15watts output on a single tube is tempting.
 
M

mik190

Member
Joined 2009
rock4016 said:
The datasheet I saw on the 6j52p had 5w plates, guess my russian is not up to spec.

How about a tube George mentioned in the 20W single tube thread.

"The 6HV5A and relatives. Transconductance is 65000, Mu is 300, plate dissipation is 35 watts. The plate is big enough to eat a bit more than 35 watts. So. it's a done deal, right? Not so easy. The tube needs a bunch of voltage, and it's plate resistance is real high, so feedback is almost mandantory. I have experimented a bit with this tube and have yet to tame it. Good luck! "

Sounds like it would be an interesting canidate that would need more experimentation, but the possibility of over 15watts output on a single tube is tempting.
Click to expand...

Very high voltage might be a problem from technical side. Especiallty for power supply. The only option I know in this case to use power supplies from microwave oven. But they get around 2000 V output.
 
Vinylsavor

Vinylsavor

Member
Joined 2002
vinylsavor.blogspot.com/
Hi!

After many years of absence, I decided to join DIYaudio again. I just saw this thread about the single tube amp and the 6HV5A was mentioned. I used this tube and it's relatives (6HS5) for various amps and preamps in the past. Just recently I published a schematic in another forum.

Here is the schematic of the amp with the 6HS5:

ImageShack® - Online Photo and Video Hosting

ImageShack® - Online Photo and Video Hosting

The required B+ can be done with a voltage double PSU:

ImageShack® - Online Photo and Video Hosting

This amp gives 7-8 W SE. It requires about 2,7-2,8V RMS on the input for full power.

Here are some pics of a finished amp with this tube:

ImageShack® - Online Photo and Video Hosting

ImageShack® - Online Photo and Video Hosting


This concepts scales well for PSE operation.

Here a pic of a PSE stereo amp besides a SE:

ImageShack® - Online Photo and Video Hosting


ImageShack® - Online Photo and Video Hosting


Recently I finished a PSE version with 4 6HS5 in parallel with 30W per channel. These have been built as monoblocks:

ImageShack® - Online Photo and Video Hosting


ImageShack® - Online Photo and Video Hosting

If there is interest, I'm happy to share more technical details.

Best regards

Thomas
 
Vinylsavor

Vinylsavor

Member
Joined 2002
vinylsavor.blogspot.com/
Hi Michael,

So far I built this concept with two types of output transformers. One is the Tango FE20-14S. The second is the Lundahl LL2735B. Lundahl developed this transformer after me requesting it and I had the opportunity to evaluate the first engineering samples.

The chokes I used are Lundahl but others could be used as well if they have the proper insulation rating for the high B+

I get the power transformers custom made to my specs. That is a universal power transformer with several taps which I use in all my power amps. Any power transformer with similar voltages could be used. Important to observe the insulation rating of the heater windings! One of them needs to be tied to B+

Note: Please be aware that I'm running a small business as a side job, offering parts, kits and fully assembled amps of all of my projects. But a lot of my designs like this one are public domain and the schematics are published on various forums free for anybody to use.

Best regards

Thomas
 
Wavebourn

Wavebourn

Member
Joined 2006
wavebourn.com
6Ж52П were made according to 2 different specs: for military applications -- lower Pd, lower noises and microphonics, and for civil specs for TV video amplifiers: higher Pd was allowed. But as far as I know, they were dying young in TV sets. I used to swap them in TV receivers by 6P15P sometimes, that were cheaper and wider available; with lower amplification factor, but higher anode dissipation rates.
 
M

mik190

Member
Joined 2009
Vinylsavor said:
Hi Michael,

So far I built this concept with two types of output transformers. One is the Tango FE20-14S. The second is the Lundahl LL2735B. Lundahl developed this transformer after me requesting it and I had the opportunity to evaluate the first engineering samples.

The chokes I used are Lundahl but others could be used as well if they have the proper insulation rating for the high B+

Best regards

Thomas
Click to expand...

Hi Thomas

What about input sensitivity of this amplifier? Is it 2V?
 
Vinylsavor

Vinylsavor

Member
Joined 2002
vinylsavor.blogspot.com/
Hi!

The difference between 2V and 2.8V sensitivity is a mere 3dB.
Yes you can increase the sensitivity with an input transformer. A 1:2 transformer would bring it to 1.4V input for full power. However make sure your preamp is able to properly drive the input transformer.

Most preamps have way too much gain anyways, so a less sensitive power amp can be beneficial.

Read up my artice about gain, headroom and power on my blog about this.

Best regards

Thomas
 
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