Author: Ale Moglia

"A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp)

6E6P-DR curves (6Э6П-ДР)

Here are some curves of this great valve I traced time ago, hope these are useful when designing a stage with them.

Unfortunately the variance of the valve’s parameters is all over the place. Hence you should use these curves as reference and not as sacred data. Luckily, I have plenty of them and can match/select pairs as needed.

6E6P-DR triode mode
6E6P-DR tracer setup

Website restored

It’s been a few painful days, however the website is now back up and running. The site suffered a malware attack and was used for phishing attacks. Who knows how it happened, despite having malware scans and used solely to blog on WordPress it happened.

Thanks to everyone who drop me an email asking for the site. I hope all the content is up there. We had to delete 65K generated PHP files and the whole thing was damaged. Thanks to my friend Nico who helped me getting this back on track.

If you see that anything is missing, please let me know.

Ale

4P1L PSE Amplifier for Sale!

Firstly, my apologies to all readers for not writing much over the last year. Things have gone a bit crazy between work and family commitments. Also, modular synthesiser work has taken a lot of interest lately to me. Finally, this blog was hacked twice and have been painful to get it back up again. Needless to say, I’m not an IT expert so I do the best I can!

Selling my beloved 4P1L

All good things come to an end. In this case, my loved 4P1L PSE Amplifier. I moved listening rooms with the growing family and space is now an issue. I no longer can store this beauty and I think it would be wise for someone else to enjoy it rather than collecting dust somewhere my attic (which is mostly full).

This amplifier gave me a lot of joy and sums up a “no-compromise” approach to DHT considering the design and component selection of the power supplies. It’s a very flexible beast as the power supplies (HT and LT) can be used in many different configurations – all the way up to a 300B and more.

4P1L PSE Output Stage

Full 4P1L PSE Amplifier

For the ones who remember my 814 amplifier, I reused the amazing power supplies which were feeding the 46 driver stage. The DHT filament raw supply is similar to these:
One PS per channel (2 boxes on the right in the picture above)
It’s a no-compromise design here. Best custom-made JMS transformers designed to fit this amp supplies with split-bobbins and copper screening.
The HT supply is my design for 300B and 4P1L PSE. It has a lot of capacity which can be reused and is very flexible with its design. It has a surge protection start up circuit and two current meter (one per channel).
I will dig out the circuit and share all documentation for whoever buys this  amplifier.
The amp use MM OPTs, 4mm plate machined by Schaefer.  Filament bias and circuit as per own my design.
All cables provided.
4 valves selected and matched to gm and Ia by me with eTracer
You will need a preamplifier / driver – which isn’t included. Anything with gain of x8 will work (preferably a DHT stage like 01a, 26,4P1L, 2P29L, etc.) – this isn’t included.

 

This is “the one and only” Bartola 4P1L amplifier. It has gone back and forth to ETF.18 and got into quarter finals on the competition (personally and a few others think it could have gone further but listening levels and setup were not the best).

Needless to say:

  • No reserves
  • Payment upfront
  • Only collection in London, UK.  No deliveries
  • Sold as-is. You need to know what you’re doing here 🙂

I haven’t got idea of what price to ask, need to think about it.

If you are interested, ping me.

Cheers,

Ale

Bartola Valves Book Scam!

It’s been long since my last post. Life is busy for me these days, so not much time free for Audio work. I managed to rebuild my listening room after nearly a year of disruptive and delayed building works. So am a happy man on that front.

I hope I can upload some work soon. In the meantime, my friend Geoff raised to me this particular scam, unbelievable:

https://archivebooks.online/download/4677785-bartola-valves-all-about-electronic-valves-and-hi-fi

Amazing to see that there are people out there trying to get your details with this. I can’t even imagine what they are expecting you to do after registering in order to download allegedly some “book” which I never wrote or commissioned.

Anyhow, you’ve been warned. Don’t even it 🙂

6P36S Mono SE Amp

Brief post of a very long experiment. Unfortunately I’d have to dig out a long list of notes, tests and simulations to get the full thing out there. Unfortunately due to constraints, this will be brief but I hope it’d be entertaining.

6P36S SE Amp

Continue reading “6P36S Mono SE Amp”

811a SE Amplifier with a twist

Goodbye Jon

Sadly, yesterday heard the sad news that our friend Jon Finlayson from the London Audio Circle passed away.  Jon was an incredible person, a true music lover and passionate about life. He introduced me to most of the circle team members and enjoyed thoroughly the meeting at his place and listen to his electrostatic speakers and constantly evolving system.

I learnt such a great deal of stuff from him and will remember our conversations and how passionate and meticulous he was into doing things. In particular when I built my Starlight CD player and he helped me out with the DAC ladder resistor matching.

See you on the other side Jon.

The 811a amplifier

The last year of the pandemic allowed me to do some experiments whilst being more at home. I hooked up an 811a on the bench with the following circuit:

I reused my original D3a driver from the 300B SE Amplifier. That was an easy choice and speed up my building process. I added a PMOS driver for a “plate to grid” feedback. The feedback network was somehow tricky to trim as had limited resistors available but the combination of 2 39KΩ resistors and a 18KΩ resistor worked well. The follower helped with driving the positive grid current which is about 16mA on idle at 22.5V bias or so. The bias is actually adjusted with a positive regulator set to about 50V on the PMOS gate.

I ended up building a PCB for the PMOS driver, very simple but effective.  I used an SMPS for the filament supply and was good enough for testing purposes.

The iron was some Lundahl gapped at 90mA which I had at hand, but can be anything you want.

Power? Oh yes, could extract 16W at about 1.5% and think measured 18W before clipping.  Distortion at low power (e.g. 2W) was less than 0.4% so a nice beauty to listen to. I love the sound I got out of it, not my normal listening system and couldn’t move the whole Frankenstein down to where my speakers are with the kids around and 600V all over it (long are gone those days where 600V were everywhere in my music cabinet).

 

 

24-A Driver

About 10 years ago I used this tetrode driver which I loved. The 24a. It has hungry filaments, albeit a lovely sound. I probably lost a few readers by now, but don’t care. The 24a into the 45 Single ended, was a great choice, no wonder why Torsten praised this valve.

I settled with the following driver which worked well for me. The 24a is carefully operated at 8mA and 80V on the screen to minimise distortion. This way you can get about 35.5dB (x60) gain stage with about 160Vpp output at 0.5% THD. Yes, more H3 component than a triode, but sounds really nice:

 

Simple and effective gain stage for a 2-stage amplifier. The output valve could be anything of your choice: 2A3, 45 or even 300B.

The hybrid mu-follower use R1 to set the gain of the tetrode stage (I covered this before many times) and the stable mu-output also feed the screen regulator (Reg 1). I made also a PCB for this regulator, so the driver footprint is very small.