PSU3 and Phono3 build

[Richard]

Hi Freddie,

Yes, Edicron EI Yugo ECC83 with the flat plates, very dynamic, some might prefer something softer perhaps but I like them and can't think of any with a better bass.

You'd put 220uF 10V caps across the first stage cathode resistors. Oscon or Blackgate would be nice but I used a standard type and found much the same effect. There is an increase in gain as you say which with the loss from using 5751 equates to almost the same gain as ECC83 without bypass caps.

K5881 is very sensitive, what pre are you using?

[FreddieT]

Hi Richard,

Thanks. I'll give the 5751/by-pass a try. I did track down some Black Gates for the K5881 last year on ebay so maybe I'll try my luck again.

Looks like I got lucky with the EI valves; I wouldn't want anything softer especially after putting PIO caps in the K5881 for the 5881 coupling to the phase splitter; they improved the bass but robbed the dynamics a little compared with the polyester films I replaced. That said, they seem to be settling in nicely and my neighbour was pleasantly surprised the other evening having not heard the amp for a couple of weeks - so I may not be imagining the improvement.

I'm using a passive pre of my own construction (ALPS Blue shunt wired after talking to John Caswell + selector switch in a box). The K5881 has the MKII mods giving 75mV sensitivity. I have wondered about a CF buffer stage powered from the Pre3 socket on the PSU3 - maybe I'll try it one day! Suggestion for the best triode for that job anyone? I notice that this month's HFW has reviewed a Ming Da pre amp using 300Bs as buffers - seems a little strange to me.

F.

[Richard]

Hi Freddie,

BGs would be nice, we used Oscons from RS.

I would have gone the route of polyprops rather than PIO for coupling in K5881. Some polyprops can be a bit tinkly but the Soniqs are very good all round.

Pre3 would be good plugged into the Pre3 socket on PSU3 You have plenty of sensitivity though and could knock it down a bit. I'd be tempted to try a 220K metalfilm in series inside the amp, after rca and before the 100K gridleak of the input which will reduce it to 225mV.

[FreddieT]

Hi Richard,

I think I'll give the polyprops a try if it will add back the dynamics and top end without stealing the bass improvements from the PIO.

F.

[Pingushome]

Hi Greg, was intrested in your pre II. I have only just got back into hifi but have had a pre for some timeand feel that a change may be useful so as I am a complete novice to electronics (can use a dmm an follow a cir dia just) may i ask advice pls. what internal wire do you use and is ther a simple circuit for the pre that I can follow?
I found wiring the pre select switch a real pain but looking at your and bobs pres there seem to be plenty of space in them without the o/p trans.
Any help would be really appreciated.
Martin

[Pingushome]

Hi Bob, am a bit of a novice in electronics (can use a dmm and follow a circuit,just) but really liked your modded preII and would like to try it, have you got any info about the bits on the board and how they are connected. I am just about to rebuild my psu as it has failed so converting that is no probs.
Any help appreciated. Martin

[bob orbell]

Hi Martin, just to put the record right, mine is a PRE3 case with PRE2 board the input is controled by relays from PRE3. The C/D can be found in the FAQ under (upgrades and tweeks) I think you will find it very hard to get a PRE2 PCB now, infact Colin Hepburn posibly had the last in captivity, from me, but you could build one on some matrix board, have you considered PRE3 as a kit? it will work from PSU2, with component change and is very good and simple to build. Component wise for a C/F any good quality film and foil capacitors to the correct value will be fine and I used carbon film resistors, because metal film were too bright for me. Hope this helps you. BOB

[Greg.]

Hi Martin,

My input/output signal wires are hard wired in. This is Pre II so there is no relay board.

For input and output signal wiring I used IPL Acoustic IC2. In my system, silver plated copper works well.

For the internal signal wiring between switches, I used IPL HU1.

Link here for both cables. http://www.iplacoustics.co.uk/ipl_cables.htm

Wire from the power source and between the board and the valve is 0.7mm silver plated OFC, PTFE insulated. Supply options have changed since I did it but this stuff will put you in the 'ball park'.

http://www.wires.co.uk/acatalog/cu_sp.html Just scroll down to 71mm silver plated copper wire.

Hope that helps,

Greg

[Pingushome]

Hi Bob and Greg,
Thanks for the info. Sorry for the delay in reply things gotn in the way, like work.
Have now got a new tx from Mathew and the pre two is working ok. I think I will go down the road of a cf a' la Gregs unit in the future so I may be asking you a few questions later Greg, if I may. At present I am having difficulty in finding good caps at a reasonable price especially the 47nf one...any ideas would be appreciated, I have ordered the wire from ICL and resits form HIfi Colective but where can I get the caps?
Martin

[Greg.]

Hmmm, Martin, sorry, don't understand your questions. Give me some time to re-read the whole thread and then maybe I can help.