audio-talk

pre65 · Posted: Fri May 15, 2009 9:09 am Post subject: 829b PSE

The next project will be 829b PSE,as the experiments with 832a PSE were quite sucessful.

I have a couple of guitar amp chassis,two huge mains transformers and two used QQV06/40a (829b equivalents) so the majority of parts are to hand.

Andrew I is getting me a couple of his HK 27H/200ma chokes for the power supply and the rectifier will be a hybrid bridge wiv me old favs 6D22s.

Suggested layout is as per piccie. Any comments ?

http://i111.photobucket.com/albums/n146/pre65/829bPSE.jpg

I was going to use my 6CG7 as the driver but am leaning towards a 6SN7GT for visual reasons. What is the recommendation on those Mr Bass as you have been reading up on them ?

Dave the bass · Posted: Fri May 15, 2009 9:27 am Post subject: Re: 829b PSE

pre65 · Posted: Fri May 15, 2009 10:06 am Post subject:

I've got an inexpensive pair of e-bay to start with.

Yes,eggy fest should be no problem as long as they turn out right !

In fact the car may be full of amps if I'm not careful.

Part of the "butterfly" brigade no less.

Wink

Dave the bass · Posted: Fri May 15, 2009 10:12 am Post subject:

I've got a Quad of Sylvania 6SN7's if you'd like to borrow then sometime Phil, just ask.

I wont have much room in the car what with bringing the Sabs and Colin's Woolfelt so the only amp I'll bring is 6B4G LW with CC heaters and 83 MVR for appraisal. I think its a great 'rock' amp but lacks the finesse of C3g-2A3.

Get buildin' GrandPaps Laughing

DTB

pre65 · Posted: Fri May 15, 2009 12:05 pm Post subject:

Max N · Old Hand Joined: 16 Aug 2007 Posts: 474

This is paraphrasing from MJ:
6sn7 are capable of very low distortion, but ideally they need to be run at around 250V, with about 9mA through them. At that sort of operating point, the main source of distortion will be varying anode resistance. To minimise this, you need a big anode load resistor, say 50K or more. 9mA through 50K requires 450V. Add this to the plate volts, and you get 700V HT.
If 700V isn't available or convenient, use an active load (CCS) or anode choke.
I like 6sn7, but they aren't the easiest valve to get the best out of.

pre65 · Posted: Fri May 15, 2009 3:43 pm Post subject:

Hi Max-if I used anode chokes would I need one for each triode half (ie 2 per valve).

Looking in the spares box there are four (4) Hammond 156C chokes (150H @ 8ma DC) so are they any good ?

Mike H · Posted: Fri May 15, 2009 8:33 pm Post subject:

Ey up those traffos look familiar...

6SN7 with choke loads, yeah why not? No probs with resistor drop and stupid supply voltages, sorted. One per triode, yes (2 per valve).

As a guide 6SN7 gain is like e.g. ECC82.

Where those boxes come from?

pre65 · Posted: Fri May 15, 2009 8:47 pm Post subject:

Mike H · Posted: Fri May 15, 2009 8:56 pm Post subject:

Oooo...

Bloody hell is that all, 3 quid? Shocked

pre65 · Posted: Fri May 15, 2009 9:00 pm Post subject:

Mike H · Posted: Fri May 15, 2009 9:05 pm Post subject:

That's more like it!

You know what it is I mustn't scroll down at the same time. Very Happy

pre65 · Posted: Sat May 16, 2009 8:17 am Post subject:

My 6SN7 GT came this morning,and they are actually 6H8C (I knew they were Russian).

Reading up on the interweb it seems they are regarded as quite good and a suitable replacement for the 6SN7.

Not bad for £7 a pair inc P & P,and they came from Kent !!

ed · Posted: Sat May 16, 2009 9:14 am Post subject:

I'm pretty sure they are the same as shuguang 6N8P......

I may be wrong but the last time I bought some 6N8P they came with 6H8C printed on the glass.....they were certainly cheap, they sounded nice, but as I recall one or two of them wouldn't stand vertically....

Max N · Old Hand Joined: 16 Aug 2007 Posts: 474