QQV07-50 PP amp

[ab0ez]

Hey gang,

Been out for a while recovering from hernia surgery. No, I didn't get it lifting tube amps or khorns, but, believe it or not, I blew my nose hard enough to split my guts open! What fun!

Here is what my 832A monoblock amps that were previously posted have morphed into. The sound is excellent, bass outstanding on the khorns. And, best of all, it is very, very quiet, not a trivial thing with 104-105dB efficient speakers. I'm pretty impressed with the sound of the QQV07-50 as a push pull output tube.

The chassis is a Hammond AO-39 organ amp. You can get them for well under $100 and sell the 6BQ5's to recover some of the purchase cost.

Operating conditions are:
~370 volts on the plates.
220 volts on the screens.
each tetrode section biased at about 46mA idle.

 

[djnagle]

Very cool looking amp. Did you build two or are you going mono?

 

[ab0ez]

I have two of them for stereo. Right now I'm checking them out on an SACD of Edgar Winter's "They only come out at night" album. Pretty impressive.

Here is what I started with:

 

[ab0ez]

Here's a shot under the hood.

 

[jon_s]

Been out for a while recovering from hernia surgery. No, I didn't get it lifting tube amps or khorns, but, believe it or not, I blew my nose hard enough to split my guts open! What fun!

Holy cow! As a notorious noseblower, I now have a new worst fear.

 

[ab0ez]

Brother, you're telling me! To make it even more bizarre, I am an exercise freak. I lift weights, run, am not 100lbs overweight, etc and it still happened. Blasted genetics.

 

[ab0ez]

The finished amps, showing one of the two monoblocks (both amps have the 3rd choke) with and without the 3rd choke and now running 5894B output tubes. They flat out sound better than the QQV07-50 tubes.

 

[Shadowdog]

Hope all goes well after that surgery!


So the output trans are those small ones at the end of the chassis by the neat output tube! Must be fairly low watts.

Thanks!

 

[ab0ez]

Thanks Shadowdog. Shoulder replacements are no fun, but my shoulder is an order of magnitude better than before, as is my pain level and ability to use my left arm again.

As far as power output for the PP monoblocks, about 18 watts, which drives my modded KHorns to earschplittenloudenboomer levels. The amps sound fabulous, with outstanding bass, resolution and smoothness. They sound like a 6BQ5 PP amp with better bass, and improved clarity and imaging.

A friend of mine offered to buy them at a VERY good price. My wife said to him "no way!" She likes the sound of those amps! They power my rear Khorns in my sound room.

 

[knockbill]

Cool,,, I have a pair of 829Bs,, looks like they could be used in a similar way,,, PP in the same bottle?

 

[ab0ez]

829B tubes are similar to 6L6 tubes, with the exception of the lower screen grid voltage rating. Like the 5894, QQV07-50, 832A (same for the 6146) and other tubes from the same "family" they need to be run with a regulated and adjustable screen grid voltage source.

Other than that, they are GREAT audio tubes!

Yes, the 829B is two tubes in one bottle!

 

[knockbill]

Thanks for replying,,, I found a couple of schematics which put the plates parallel,,, your plan looks to be PP, at least the OPT is,,, Maybe your schem can be modified to use 829s.. I have PP output tx,,, low on SE , tho... nice job on your amps...

 

[ab0ez]

Yep, my amps are PP. The schematic I posted was what I started with. Since then I've added chokes and a regulated and adjustable screen grid supply.

 

[knockbill]

thanks again, i'll try your schems....

 

[ab0ez]

Use it as a starting point and go from there. See how good you can make it! Feel free to ask me any questions.

 

[knockbill]

Appreciate your offer! Got the tubes last year, and got sidetracked building an 811 SE amp, which is ready to be transferred to a chassis,,, This one will be next!
Thanks again..

 

[ab0ez]

100% my pleasure to help in any way I can. BTW, I also have some 811A tubes just begging to be used. Great minds think alike.....even if mine is a bit warped!