Tube Amplifier and Tube pre-Amplifier Builds

[radium7]

Can you provide some more details around sound signature and listening impressions with rest of your chain? Also for each project a tentative cost would be helpful

i will give more details and cost from my next post

 

[radium7]

Local made choke with interleaving papers for each layer in paper bobbin - old method of winding

 

[radium7]

pune based transformer manufacturer BTC- very famous in olden days and produce very high quality transformers.

 

[radium7]

Mumbai based transformers producer ARGO. 150ma 10H choke. see its build quality.

 

[radium7]

Recently bought Lundahl LL2766 OPT which has air gap adjusted to 40ma for using with 45 tubes.

 

[all4music]

wow! Lundahls!
where did you procure them from!?

great going with the builds!

 

[radium7]

from K & K audio USA.,

 

[GeorgeO]

Very nice builds and should inspire some lurkers to take the leap into tube sound.
Good luck!

 

[reubensm]

For 2xEL 34 based push pull designs, what output transformer types do you recommend? I have a couple of old voltage stabiliser transformers and was contemplating repurposing them for a hand winding job. Plan to use carefully repurposed copper wire salvaged from old refrigerator compressors. All maverick ideas but this is going to be a big project so appreciate whatever help I can find

 

[radium7]

For 2xEL 34 based push pull designs, what output transformer types do you recommend? I have a couple of old voltage stabiliser transformers and was contemplating repurposing them for a hand winding job. Plan to use carefully repurposed copper wire salvaged from old refrigerator compressors. All maverick ideas but this is going to be a big project so appreciate whatever help I can find

for 2XEL34 in push pull ultra linear mode, auto bias you may need OPT with following spec:

Power handling capacity: 30 Watts (min)
primary impedence: 6.6K
Secondary impedence: 4, 8, 16 ohms
43% screen tap
primary inductance : 10H (min)

for 2XEL34 in push pull ultra linear mode, fixed bias

Power handling capacity: 40 Watts (min)
primary impedence: 5K
Secondary impedence: 4, 8, 16 ohms
43% screen tap
primary inductance : 10H (min)

for 2XEL34 in push pull triode mode, auto bias (Pure class A)

Power handling capacity: 25 Watts (min)
primary impedence: 10K
Secondary impedence: 4, 8, 16 ohms
43% screen tap
primary inductance : 10H (min)

Pentode mode gives more power with distortion suitable for guitar and PA amps.

These spec are based on details in the tube datasheet and commonly used in amps.
but it may slightly vary according to the circuits. you have to check with circuit you are following. Didn't have any idea of reusing copper wires, normally the transformers build with such used copper coil have short life. but the cores from old transformers are very good and far better than the core we got now a days. i have used lot of old cores.

 

[GeorgeO]

I also tend to agree. Using wire of unknown provenance to wind OPTs and expecting good performance is risky. Any chain is only as good as it's weakest link. As it is OPTs of good quality are only offered by a handful of vendors, which makes me think that there's more to it than is apparent.
However, do experiment, and key is know the results.

 

[Mayank Shah]

Work of art. Admire your passion.

 

[radium7]

Building EL11 + EBC11 + 5Y3 Tube amplifier.
EL11 elder brother of famous EL34 is one of the best and rare power tube capable of delivering 5 Watts in triode mode.
used local and imported components
EBC11 are very rare telefunken brand tubes in sealed packs.
All tubes are Nos tubes.









Tubes used in the amp

 

[GeorgeO]

Please tell us about newer builds that you have done or are doing.
Thanks

 

[radium7]

Finally I got one of the Cine Amplifier which was built by my guru late Krishnamurthy. But in a very bad shape. He had built nearly 150 such Amplifiers for Theaters, lodges, Houses. He followed the famous Mullard 520 circuit with few modifications. EF86-1, ECC83-1, EL34-4, 5U4G-2 tubes for each channel.
Output stage is PPP type and operated in ultralinear mode to deliver 60 Watts output power. Mostly connected to Altec or Goodmans speakers. For Home listening the output stage is operated in Triode mode and delivers 30 Watts of very sweet sound.

Bottom section is the Left channel, next right channel, Power control panel and the top section is the Pre amplifier section (Mullard 2 valve circuit with few modifications).

The amplifier was damaged, particularly the preamp section it has to be changed and one side cover is missing, I can not use any of this transformers or components again, all are in very bad condition and just i am going to take the chassis alone.
I have few components in hand need to place order for other components and transformers. Going to use custom made transformers only, because we have all original winding data for this model and my winder has wound lot of this model transformers.

I will post all work involved in restoring this amplifier.

These are the few pictures of Amplifier

 

[radium7]

This one was serviced by some local Mechanic.

 

[radium7]

Some local mechanic closed the EL34x2 5U4gx2 tube socket holes


Bottom Left Channel


Right channel


Preamplifier stage.

 

[reubensm]

any update on the cine amp project?

 

[Hari Iyer]

Hope my 300B tube amp re-built project sees the light of the day in future.....

 

[radium7]

any update on the cine amp project?

Painting of the chassis is completed.
Almost collected all the components, Solen Fast power stage capacitors, AB Resistors, Kiwame Resistors and Mills resistors.
QQQ tube sockets are in stock, Alps Pots, etc.,
Need to get the Transformers.
Due to some personal issues all my projects delayed, now started finishing one by one.
will update soon