QQV who?

shane · Post by **shane** » Mon Dec 10, 2007 7:11 pm

I've just been given a dirty great big box of old valves, mostly unidentifiable, but in amongst them is a virtually unused pair of QQV07-50s (details here http://www.r-type.org/exhib/aad0173.htm ). I understand that these are an update on the theme of an 832, so could they be used to build a PP? If so, what sort of ironwork would be needed?

pre65 · Post by **pre65** » Mon Dec 10, 2007 8:24 pm

Hi Shane-the 832A was my first amp and for the output transformers i used a pair of Hammond "universal" 125D .

I now use Audionote Trans 200 which are 8K ohm.

As the Hammonds are not being used at the moment would you like to borrow them to get your project going ?

For the power supply i used a toroid transformer with two 200v secondaries and went for just a cheap bridge and 820uf cap for each channel which gives (according to Andrew I ) a robust and powerful supply and seems to be preferable to his version with a valve rectifier !

Only other thing of note is using an LM317 on each dual cathode to give a CCS supply instead of the cathode resistor and cap.

So let me know if you would like the output transformers,and i could also give you two 820uf 450v caps which have been used,but only for a couple of hours (i bought four originally)in the ECL82 power supply.

http://www.tubecollector.org/qqv07-50.htm

http://tubedata.itchurch.org/sheets/129/q/QQV07-50.pdf

pre65 · Post by **pre65** » Mon Dec 10, 2007 11:17 pm

Hi Shane-i have been reading about the QQV07-50 and it may be more like an 829,which is the bigger brother of the 832A.

Either way i'm sure it would make into a PP amp but you might have to play with the circuit to suit its particular parameters.

The 832A circuit that seems to be more commonly used is

http://www.audiohobbyist.com/projects/832.htm

shane · Post by **shane** » Tue Dec 11, 2007 7:37 am

Hi Philip, that's very kind. I'll PM you.

pre65 · Post by **pre65** » Thu Jan 03, 2008 11:55 am

Hi Shane-the QQV's came this morning.Thanks.

I feel that they are not really meant to fit the Septar bases as the 832A does.

They do fit but the pins dont go in quite far enough due to a small lip on the base.

However they do just fit !

I fitted a pair but one channel was very fuzzy,so after swapping around between the 4 i ended up with a good pair.

Now playing some Elanor Mcevoy and it sounds good !

So i would say that they DO work in the 832A circuit although i suspect there is a slight difference in the sound.Is that due to the valve ? Or perhaps the circuit needs tinkering with ?

Dave the bass · Post by **Dave the bass** » Thu Jan 03, 2008 12:06 pm

You be carefull...that looks like Nick/Paul/Darren stuff to me!

DTB

shane · Post by **shane** » Thu Jan 03, 2008 12:08 pm

That was quick work Philip! I wasn't sure what sort of condition they were in, so it seemed like a good idea to give you a selection. I've still got half a dozen to choose from.

How would you describe the difference in sound? Better, worse or just different?

pre65 · Post by **pre65** » Thu Jan 03, 2008 12:20 pm

Hi Shane-i would say the sound is the same !

I still feel that perhaps they are nearer to an 829 because they have more gain shown as the shunted stepper on my Pre3 now only needs to be on 3rd click to be reasonably loud.

Perhaps one of our more "theoretical" friends could examine the QQV and 832 parameters and suggest some mods to the Autohobbiest circuit.

I will play some more mooooosic and see if my opinion changes.

Darren · Post by **Darren** » Thu Jan 03, 2008 12:21 pm

Dave the bass wrote: You be carefull...that looks like Nick/Paul/Darren stuff to me!

DTB

And !!!

Dave the bass · Post by **Dave the bass** » Thu Jan 03, 2008 12:22 pm

Darren wrote:
Dave the bass wrote: You be carefull...that looks like Nick/Paul/Darren stuff to me!

DTB
And !!!

Fizzle-pop-bang-ooooofff

DTB

pre65 · Post by **pre65** » Thu Jan 03, 2008 12:25 pm

Comparison of valve sizes !

shane · Post by **shane** » Thu Jan 03, 2008 12:25 pm

Is this the original circuit you used?
http://www.audiohobbyist.com/images/832/832sch.jpg

Darren · Post by **Darren** » Thu Jan 03, 2008 12:26 pm

I see, do you have any references to such events?

Now, I'm not saying there arn't any mind you...lol

Dave the bass · Post by **Dave the bass** » Thu Jan 03, 2008 12:27 pm

pre65 wrote:Comparison of valve sizes !

Blimey, they're bigger than you! You're looking a bit sad and green today BTW, winter Blues?

DTB

andrew Ivimey · Post by **andrew Ivimey** » Thu Jan 03, 2008 12:29 pm

The secret to getting a great amplifier out of these unlikely but gorgeous looking little valves is .... the PSU. forget the output transformers - this is the world of PP.

I thought I'd be cocky, sophisticated and altogether worldywise so went for a rather nice valve PSU.

I shouldna' have bothered.

Using as many milliamps as you can muster, through a silicon bridge rectifier and a couple of monster caps and Bob's your proverbial parent's brother.

With valvePSU the amp sounds very nice but lacks a certain welly.

Philip got it right first time. He was lucky

audio-talk

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