Newby first build amp 832.

[NickG]

Thank you. I did wonder if I knew what I was doing.

[Primalsea]

Phil,

That looks very neat for a first amp. When I first started building amps I spent ages getting everything to look right and paying much attention to spacing of components. I then seemed to loose this in mad rushes just to get projects working. I soon realised that that I had the right idea in the first place. Work slowly and neatly and if it does'nt look right then strip it down and redo it.

Often now when I open up an old project I'm suprised at how neat I done it rather that in the past when I thought "what a mess, ooeeer".

Looks great, I would love to hear it going at some point.

Paul

[Paul Barker]

Let's hope nobody asks us what we're doing, 'cause we don't know.

[andrew ivimey]

In the true spirirt of not knowing what I am doing, I switched on my (P)SE 832 amp this evening.

I bought a quad of these lovely looking valves about 9 months ago and forgot about them. I'd seen the push pull project that Philip has embarked upon and it had attracted me too. The quad of valves cost me about £8 inc p&p from Ukraine. I had a spare pair of sockets as they are the same as 6C33.

Well I don't like push pull so thought what the heck! why not just sort of cut the schematic in half and bingo, SE. And I used a 6SN7 as driver because that was what I had to hand. The driver is more or less what JElabs use with almost every DHT I can think of, tailored to my HT. This was all very 'sort of more or less'. PSU was 250volts of ss bridge rectifier and caps.

I switched on.

One 832 glowed a beautiful blue colour (internal heater / cathode short?) and the sound died quickly, so I put another valve in. On the other channel a 6SN7 from China via the garden shed also didn't appreciate the voltage and conked.

The amp as was also didn't like parallel SE but with only one anode connected, it wasn't bad at all. Oh there are a number of (solvable, I am sure) problems but the sound was close to being very acceptable.

So with a decent design (i.e. not mine) and a little care and attention, it could be a very decent and unusual looking amplifier.

Philip, in push pull mode (so more power!) I think you could be onto a winner. The potential is clearly there.

[pre65]

Hi Andrew-i dont know how some of you work so quick !

spurred on by your efforts i thought i would try and get it working tonight as i had got my missing resistors/capacitors from Bluebell this morning.

but i seem to still be short of a couple of resistors so i will have to wait again.

anyone got two 390k 2w metal films spare ?


Philip

[Primalsea]

Phillip,

I have 240K + 100K, or I have 2 resistors that measure about 435K. If they will get you by for the weekend you are welcome to them.

You can come and get them or I can post them.

[pre65]

Hi Paul-thanks for the offer,but i will take up Matts (LORD) offer on this occasion.

Another thing that i had forgotten to source is some form of connector to connect the output transformer wires to the top pins on the 832.

i was going to use small "chocolate block" connectors but ive cut the wires a bit too short (what a dick)


Philip

[Paul Barker]

You mean you cut the pins at the top of the valve? You aren't supposed to do that.

Wire wrap is all I can think of.

The connector used in industry (ship to shore radio) is like the metal part of a connecting strip, obviously the nylon 6 couldn't tolerate that amount of heat. The block connector has the added advantage of dissipating some anode heat. Better practice is to use a finned connector to dissipate heat.

The glass on types with rigid pins sticking out like hedgehogs is very prone top breakage, the act of cutting the pin could easily make it gassy.

[pre65]

Hi- no not the actual valve prongs,just the output transformer wires !

Philip

[Paul Barker]

Crimps bought from electrical wholesalers. Blue ones probably.