Love to see some pictures ....
Love to see some pictures ....
Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)
I see you are using an 834P. Now you have a stellar power amp the 834 can be improved quite dramatically as well with some simple mods, see http://theartofsound.net/forum/showt...563#post993563
Very well done! It Takes Nuts to purchase such a poorly conditioned Amp in the first place, no matter it's reputation. David Coe's work, commitment to a project and passion is top notch and I know he wouldn't rest until he'd cracked it and had it seriously singing.
10/10 all round chaps! Picture please!
"lack of passion is fatal"
Vinyl: Thorens TD-124mk2 / SME-312 Aluminium 'special' / SME M2-9R / STEREO: Etsuro Urushi Cobalt / Shure M3D / Ortofon SPU A95 / Cartridge Man Music Master / Shure - SC35C (US) / SAEC C3 MC MONO: Miyajima Zero B 0.7mil mono / Miyajima Premium 1.0 / Amps & SUTs: Radford STA25 mk3 / AD Audio 'Satchmo2' pre & LCR phono / Hashimoto HM-7 SUT / ETR-MONO SUT Digital: Audio Note 4.1 (with DAC5 upgrades) DAC / Roon / Tidal Speakers: Tannoy 12" MGs' in RFC custom 'Rutland' Cabinets with RFC crossovers / Tannoy ST-100 Super Tweeters Cables: LFD Grainless phono / RFC Mercury / Duelund DCA16GA tinned copper / Kimber 12TC / SW1X Audio Design USB-SPdif / Duelund DCA20GA interconnects / SW1X Audio SPDIF Aero 6 / Mains Power Conditioner / Box Furniture rack / Audiodesk Systeme Vinyl Cleaner / a very beautiful & understanding Wife!
Location: London
Posts: 313
I'm David.
Thanks for the compliments Guys. It was a great fun project, and, I too, was surprised by the sound quality produced by this beast. I've got some photos of the insides which I'll post when I get a chance. I'd like to thank Will at Radford Revival for lending a friendly ear for advice along the way! The biggest challenge was actually something stupidly simple: the bias voltage was incorrect on one channel which had had a meltdown previously. It's a simple circuit and despite replacing all the solid states bits it just wouldn't produce the correct bias. It turned out after a detailed comparison between the working and non working channels that it all boiled down to one transistor which was new......I had been supplied a BC213A and not a BC213L. These are essentially identical but with different pin outs And the print is only visible with a magnifying glass!
Pics to follow
Location: London
Posts: 313
I'm David.
Not much to show pics-wise from my end - it's a big black box! But here's a couple, one round the back showing the 4 NOS GEC KT88s currently singing happily...
I'm sure David will post some shots of the juicy stuff inside in due course... I don't want to mess with the cover which is screwed into place and quite awkward to remove.
Thanks for the tip regarding the EAR 834p. As far as I know its un-modded, altho' it does have rolled tubes, which were in it when I bought it from RFC Paul. A Mullard and a couple of triple mica Philips 12AX7s if memory serves. I tried Telefunkens in it but didn't hear much of a change tbh.
I'll look into the Thorsten mods. David is currently building me a SUT with Hashimoto HM3s which I'll use to bypass the 834 MC input/internal trannies and go through the MM in. I'm keeping him busy this summer!
IMG_1021.jpgIMG_1023w.jpg
Location: London
Posts: 313
I'm David.
Hi All,
Some pics attached. The main work undertaken was:
1. Replace mains lead and plug, inc. lead retention.
2. Replace mains cable currently used as speaker cable with correct cable from output transformers to sockets.
3. Replace 4 x main smoothing capacitors.
4. Install correct mounting brackets for main pus caps
5. Replace 11 other old electrolytic capacitors
6. Replace cathode bypass capacitors with Elna Cerafines
7. Remove and rebuild the driver boards adding correct insulation on 8 coupling caps to make safe and reliable
8. Re-wire and improve earthing arrangement (currently made through oxidised tag connectors)
9. Remove and rebuild power supply board with correct mounting on new brackets and stand offs, replacing capacitors and adding insulation where necessary
10. Replace cathode resistors with Mills audio grade non inductive
11. Re-wire and insulate mains switch
12. Re-bias amp for current tubes
13. Replace broken regulators in driver power supply and rebuild to original specification
14. Replace indicator light and reconnect power supply inc. mounting power supply board correctly
15. Reflow all connections on two driver amp boards
16. Replace bias pots
17. Trace bias fault on one channel
18. Replace faulty transistors and op amps in that channel
19. Repair broken tracks and reflow entire driver board on faulty channel
20. Upgrade coupling capacitors to Leclanche /Mundorf ZNs
[IMG]Rad3 by David Coe, on Flickr[/IMG]
[IMG]
rad2 by David Coe, on Flickr[/IMG]
[IMG]rad1 by David Coe, on Flickr[/IMG]
Happy to answer any questions!
David
Good grief - that looks like pretty much like a rebuild.
Amazing quality David. I've had the pleasure of hearing some of your work and I have no doubt this Radford is similarly out of this world.
Are you inspired to do a build using similar circuitry to the Radford TT100?
Edward
Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)
Location: London
Posts: 313
I'm David.
Hi Edward, I was very impressed with the sound quality and very low noise of the circuit and in particular there was loads of grunt with my fussy Tannoy Canterburys. But being a valve man I'm thinking of doing something with the all valve STA circuit and seeing what that does with a pair of Tannoy Canterburys!
It's been really interesting turning some of my holy cows on their udders so to speak. Eg I'd always thought no feedback amps were my favourites and solid state driver stages-who'd want them in a valve amp? So seeing what Radford and others can do with properly implemented feedback and solid state opamp input stages has been a real eye-opener!
Yes that I believe Arthur Radford was so successful in his design in being able to reduce distortion to to vanishingly small levels via feedback - and oh yeah the iron grip his push pull ideas have on speakers such as Tannoys.
Edward
PS: Need to chat sometime with you on the PSU thing (the one Adam brought over) but no rush on that.
Current: [P20] Roon/Tidal > Custom PC> Chevron Paradox NDF16 > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)