Photo Gallery

[djn]

I love that old picture. I was a Radioman in the Navy for 4 years and that picture brings back a lot of memories.

 

[kissabout2002]

Finally finished OTL by Tim Mellow, I use all Russian Tubes 6C33C, 6J32P and 6N2P, all got by Ukrainian Sellers that they really take care to give me the best tubes available, also incredibly well packed they survived a journey to US and then to Philippines.

The amp performed very well, 25.50 watts before clipping over 8ohm, frequency response flat from 8Hz to 20.000Hz, I still have to test the THD but I already have a quick test and is very low.

Due the really hight temperature the 6c33c can reach, I elevated the tube socket and install a fan inside the enclosure that blow fresh air from outside inside the enclosure and the result is very promising, even after 5 hours of continuous test the chassis get warm but very acceptable, I will also test later the real temperature, but I can still touch the chassis so cannot be too hight, also very happy with the offset across speakers constant around 0.000 to 0.010 volt

Sound incredibly clean and punching bass never heard before on other tube amplifier.

All the best to everybody

 

[Diabolical Artificer]

Finally finished OTL by Tim Mellow

Excellent work, well done. Can we see a better resolution pic of under the chassis, that's the part of other builders amps I'm most interested in.

I too have bought valves from the Ukraine earlier this year from Kambremmer, an excellent service as always though he hasn't as many valves as he used to have. I sincerely hope out Ukrainian friends prevail in their struggles, Slave Ukraine.

Back to amp building is the mains tfmr a Toroidy?

Andy.

 

[kissabout2002]

Hi Diabolical Artificer, I will do close up pic under the chassis no problem, the main transformer is the Antek AN-64115 with the SS-12 Soft Start Module, and the CA-005 Steel Cover, the other is the AS-2212 all from Antek.

Acky

 

[djn]

Finally finished OTL by Tim Mellow, I use all Russian Tubes 6C33C, 6J32P and 6N2P, all got by Ukrainian Sellers that they really take care to give me the best tubes available, also incredibly well packed they survived a journey to US and then to Philippines.

The amp performed very well, 25.50 watts before clipping over 8ohm, frequency response flat from 8Hz to 20.000Hz, I still have to test the THD but I already have a quick test and is very low.

Due the really hight temperature the 6c33c can reach, I elevated the tube socket and install a fan inside the enclosure that blow fresh air from outside inside the enclosure and the result is very promising, even after 5 hours of continuous test the chassis get warm but very acceptable, I will also test later the real temperature, but I can still touch the chassis so cannot be too hight, also very happy with the offset across speakers constant around 0.000 to 0.010 volt

Sound incredibly clean and punching bass never heard before on other tube amplifier.

All the best to everybody

Looks great Kiss. I’ve been collecting parts to build one. Did you use the stock schematic?

 

[kissabout2002]

Hi djn, thank you, yes I strictly follow Tim Mellow schematic on audioXpress February 2010, I just add a soft start for the main transformer and a 1.5A slow fuse on series on the speaker path just for add more security for the speakers, also the ground is not connected to the chassis.

Acky

 

[6A3sUMMER]

The chassis is not grounded?
You never had a short on any electronic device you owned?
Safety First!
Prevent "The Surviving Spouse Syndrome".
Spouses can be replaced.

Security for the speakers?
Speakers can be replaced.

Newbies Beware

Just my opinions

 

[kissabout2002]

6A3sUMMER really sorry my bad I just did not want to go in details because experienced people doesn't need that normally.

OF COURSE the chassis is grounded to the ground grid but then I choose to do a multipoint star ground insulated from the chassis that's all.

 

[Diabolical Artificer]

Hi Diabolical Artificer, I will do close up pic under the chassis no problem

Thanks, looking forward to it.

 

[kissabout2002]

Hi Diabolical Artificer, here close up pic......thanks

 

[Diabolical Artificer]

Thanks, nice neat work & well laid out. I've used those brown Vishay resistors too, but they have probably shot up in price since the pandenmic. I see you use sleeving a lot, is that silicon sleeving ? Do you use it to protect connecting wires from heat? Saw the fan, good idea.

Andy.

 

[kissabout2002]

Hi Andy, I like when I do project like this do not economise on component, yes they a little pricy but not to much, yes I use silicon sleeve for protect the wires from the heat, maybe not necessary because I then check the temperature after hours of operating still cool under the chassis but is done, not finished yet I decide to add two small digital voltmeter for have always under control the offset voltage across the speaker even is very stable, I listen yesterday for 5 hours the amp and I am very happy with the sound, thank you Andy and update also with your project, all the best

 

[Diabolical Artificer]

Hi Andy, I like when I do project like this do not economise on component

Good policy, think most of us valve amp builders & our three legged fuse brethren do too. The heat aspect of valve amps often gets forgotten or omitted. I've had to retro fit cooling fans on some of my amps a few times. I use low noise PC fans but they don't shift much air, still, better than nowt. Good to hear your enjoying listening to your amp, that's the best test of all.

Here's my latest which I call the Big Green Amp. It's a 20W PP 6BG6GA AB1 amp. It has been the most difficult and convoluted amp I've ever built. It started out with 6146's and a valved tone control circuit. It's undergone numerous changes since then, the original OPT's I used were crap & changed, the valved tone control circuit caused LF oscillation so I built a OP amp based one, the original mains tfmr needed rewiring as well as other fun.

It has a 6CL6 triode strapped as the gain stage and a 12BH7A as the phase splitter with a CCS tail. I'll take some under chassis pics soon. Andy.

 

[kissabout2002]

HI Andy, oh wow what a nostalgia on see those beautiful tv orizontal deflection tubes, back in Italy I never came across the 6BG6GA the more common
tube was PL500 and then PL504, I never thought that tube could be use for audio purposes and actually in my bucket list I have the OTL that I just finished and an amp with PL504, so that will be next project, by the way how they sound those tubes?

Regarding tubed tone control I did a lot without problem, I wonder why you got LF oscillation, on pandemic time having a lot of time I make a bamboo
enclosure plus local Filipino wood for an amp, I will put a picture of it, I built also two different all tube Equaliser.

Ciao Andy grazie

Acky

 

[Diabolical Artificer]

I used the 6BG6GA's because I'd had them stashed for a while & they were a cheap OP valve. AFAIK they are essentially a 6L6 with a top cap but their achilles heal is their low Vg2, just like 807's. I used a regulated screen grid supply as recommended for the 807.

Re valve tone controls I couldn't get mine to work with the amp as it was which was then biased for AB2. The whole design was too complex with too many stages which I think created power supply de-coupling issues. The other thing that caused me to get rid of the valve based tone control was the ammount of de-coupling caps I had to use to prevent HV DC getting into the pots.

Here's some pics of the underside, ciao, Andy.

 

[kissabout2002]

Wow great job Andy, I like your style to keep the wiring on the side of the chassis, a question why the chassis is so green? You can rename the amp the Green Hornet Amp, I remember a funny movie the green hornet maybe 10 years ago, sorry I am just kidding, actually is a very unique looks and I always like new and bold ideas, by the why where did you get those nice VU meter?

About valve tone control I always follow a website and made plenty of them and never had a small problem, for sure you already know this website https://www.angelfire.com/electronic/funwithtubes/Amp-Tone-A.html

Ciao Grazie, Acky

 

[Diabolical Artificer]

Thanks Acky. I try to keep all the AC wiring well out of the way of any audio stages, noise is 1.5mV to 2.5mV rising to 4mV with the volume pots at max.

The green colour scheme comes partly from it being my favorite colour, I lived in the woods for a long time & British Racing Green being a British colour on racing cars.

The VU meters came out of a Tascam 38 reel to reel I scrapped years ago, I have some spare if you want a couple. If you PM me your address & are happy to pay the postage to Italy I'll send you a couple. The VU meter driving circuit is pretty simple using a quad opamp, easy to do on Veroboard.

Yep, I know that site, great site, I used one of his designs but couldn't get it to work in this amp. Probably a fault on my part rather than the design I used.

The Green Hornet, great name, I just call it the big green amp. There's a few video's on Youtube if your interested, I'm a rubbish video maker but here's the link - https://www.youtube.com/@diabolicalartificer/playlists

Ciao, Andy.

 

[TonyTecson]

832 pp amp///sounds great too....9 years ago...

 

[TonyTecson]

6c33 set...

 

[kissabout2002]

Thanks Acky. I try to keep all the AC wiring well out of the way of any audio stages, noise is 1.5mV to 2.5mV rising to 4mV with the volume pots at max.

The green colour scheme comes partly from it being my favorite colour, I lived in the woods for a long time & British Racing Green being a British colour on racing cars.

The VU meters came out of a Tascam 38 reel to reel I scrapped years ago, I have some spare if you want a couple. If you PM me your address & are happy to pay the postage to Italy I'll send you a couple. The VU meter driving circuit is pretty simple using a quad opamp, easy to do on Veroboard.

Yep, I know that site, great site, I used one of his designs but couldn't get it to work in this amp. Probably a fault on my part rather than the design I used.

The Green Hornet, great name, I just call it the big green amp. There's a few video's on Youtube if your interested, I'm a rubbish video maker but here's the link - https://www.youtube.com/@diabolicalartificer/playlists

Ciao, Andy.

Oh yes the British Racing Green how could I do not know that, so now make sense the colour of your amp, I lived in UK 4 years so I remember very well this colour, I then mover to Cork in Ireland for 10 years then move in my current location that is Philippines, I will look later your video's