2A3 pre-amp

[Cressy Snr]

[Paul Barker]

Ahh, but you didnt use el84's as anode loads, just as well you didnt. otherwise I would have to sue you for stealing my intellectual property. What do you mean you did it before? What has that got to do with it?

I am so glad you said that, thought I was heading for a banning! Might get banned elsewhere yet! But don't go there anyway except if someone gives a link to something I find myself there. Am only registered so I can view schematics.

the biggest loss to our community on the internet was when Ned gave up Vintagetubestalk around 1999. Guido Tent was there discussing his plans for a dht power supply. Steve Bench was there discussing his new tube tester ideas. Jonothan and I were kindred newbies learning from these guys and doing fresh stuff for us, discovering the joys of choke input, choke loading instead of resistance loaded. The only ccs was a c4s and the majority of people on that talk email group (Oh the Joe List had just begun too) would point you to a Kimmel pentode load. Don't here about that much these days.

Second biggest loss was triode mafia going dead. This forum is all I have left that I can be interested in! loads of places but my heart isn't in it.

[pre65]

This forum is all I have left that I can be interested in! loads of places but my heart isn't in it.

We love ya Paul.

[Paul Barker]

I love you too Phil.

There was a guy on the Vintage called CJ Paulus who was to me like I am to you these days. He disappeared after that went down as did a lot of the guys.

it was like the Joelist, private email group. Had I been wiser I would have stored the emails somehow. I doubt anybody has them.

[Mike H]

By the sounds I'm guessing this was like a usenet news group? Received by yer e-mail proggy


Back in them days it's wot we had instead of www forums chillun ..

[pre65]

So, after a bit of feverish activity, the 2A3 pre has given way to the 6AS7ga pre.

As Nick says, the self noise problem has gone.

I have a tad of valve hum now, it may be the 6AS7ga, but the one I'm using looks well worn. It was a freeby from Stuart Dean a long while ago.

I'm just acclimatising to the presentation.

[Mike H]

I'm just acclimatising to the presentation.

I know what that's like

[pre65]

I tried my other 6AS7ga this morning, and it sounded like the RH channel was cutting in and out, then I thought it was the Tocos pot. Turns out I'd been a bit messy with one of my shielded leads from pot to grid, it was a gnats too short and the shielding braid was touching the tag.

So it's powered down now whilst I make another lead.

I may have the opportunity to compare it with Andrews 26 battery filament pre tomorrow.

[andrew Ivimey]

I have some spare soviet 6AS7s. ( I laid in a stack for my OTL amp but they neither seem to conk out nor do stocks in the ExSOV.U seem to run out. I'll bring a couple over?

[pre65]

I have some spare soviet 6AS7s. ( I laid in a stack for my OTL amp but they neither seem to conk out nor do stocks in the ExSOV.U seem to run out. I'll bring a couple over?

Only need one.

[simon]

Top secret power supply, no five pages of discussion, this is my supply it is near perfect.

Don't use choke input and you banished for life.

Don't use Black Gate and you wish your mother never born you.

Or else this your design I have nada to do with your piece of dog dirt design if you miss out any of perfect detail.

Don't make commercial amp or I send Dave The Base round to play his guitar while scating round and round your estate with big air jumping ramps made from the offcuts of his big feller horns, until neighbours drum you out.
#Don't wasta my time talking about heater supply endlessly. you not know how to heat valve, I take your soldering iron away, you not worthy.

You no like my conditions? you go find a super moderator with 6v6 design instead.

PMSL Paul. Beautiful.

[pre65]

I have a little hum from the 6AS7ga filament. Would giving it a dedicated AC heater transformer be likely to help ? If so would a centre tapped one be even better ?

It would also mean that the heater no longer needed to be elevated, like the two 6V6.

[Paul Barker]

If it's induced from the HT diodes on a shared core it is much more than a little hum it is a very annoying hum. Ordinarily I don't detect hum from indirect triodes unless there is no ground reference. but maybe such a powerful heater in such an early stage may induce audible noise. So perhaps you will get a result, but I wouldn't peg a lot of hope on it!

[pre65]

If it's induced from the HT diodes on a shared core it is much more than a little hum it is a very annoying hum. Ordinarily I don't detect hum from indirect triodes unless there is no ground reference. but maybe such a powerful heater in such an early stage may induce audible noise. So perhaps you will get a result, but I wouldn't peg a lot of hope on it!

At the moment I'm using the 6.3V tap of the mains transformer to heat all 3 valves. Two 6V6 at 0.45A each and 6AS7ga at 2.5A. Because the 6V6 need lifted heaters all 3 are lifted. I created a virtual centre tap to get the lifting voltage in, so how can I reference them to ground ?

[Paul Barker]

you will have done that with your resistor network that lifts the DC potential. I presume you bypassed the resistor which goes to ground with a cap?