Where are the 833 amps? - Page 29

pre65 · 12th August 2011, 10:54 PM

I have a pair of 833a monoblocks. Currently undergoing mods to take them to mk3 version.

rcavictim · 13th August 2011, 12:08 AM

Quote:

Originally Posted by pre65

I have a pair of 833a monoblocks. Currently undergoing mods to take them to mk3 version.

I can feel the radiant heat from here across the pond! Safety aspects aside, that's definitely a fun project! How high is your killer B+ ?

pre65 · 13th August 2011, 06:01 AM

Actually, it's not that high.

I was advised that 1,000V was minimum for good results, but with the PSU bits I had to hand iv'e "only" managed about 950V HT

First version used my 300b SET amp via a 5K output transformer on the 16R tap to drive the 833a grid, sounded very nice. Version 1A used a small interstage transformer at about 1 :4.5 ratio, but that was less successful.

Current version (mk 2) uses a 6SN7 and EL34 (as cathode follower with fixed negative bias) to drive 833a.

Next version will give a negative supply to the EL34 cathode to correct a slight anomaly on the waveform that the scope found.

Philip Ramsey (Bluebell Audio) is trying to get Hammond to make some special interstage ( about 6:1 from memory) driving transformers, as he thinks that is the best way. I'm sure going to want to try them when (or if) they become available.

101audio · 9th February 2012, 11:43 PM

I don't think this circuit going to work, but I am going to post here and asking for your input.
I want drivers and output tube use the same DC supply. Keep power supply simple
Thanks, 101Audio

Peter 807 · 26th December 2012, 04:05 PM

Why nog make an 4CX250b SE -Amp,about 65Watts and 1000-2000 V ,Anode,grids stabilized.
Big Supply transformator end Big SE trafo.
Used an ECC83,and an EF183 for drive.
Searcing for trafo will be difficult,but fun.

Also PP is possible Output would be around 200Watts,8Ohm use an 4 Ohm tap,to drive the 8Ohm will make an very stable Amplifier,with around 85Watts.

For more info please contact me.

26th December 2012, 04:05 PM	#285
Peter 807 diyAudio Member Join Date: Dec 2012 Location: Holland	High power Amp Why nog make an 4CX250b SE -Amp,about 65Watts and 1000-2000 V ,Anode,grids stabilized. Big Supply transformator end Big SE trafo. Used an ECC83,and an EF183 for drive. Searcing for trafo will be difficult,but fun. Also PP is possible Output would be around 200Watts,8Ohm use an 4 Ohm tap,to drive the 8Ohm will make an very stable Amplifier,with around 85Watts. For more info please contact me.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
For Sale: Tube Amps, Class-A Amps, BG Ribbons, Chassis and Other Goodies!	opc	Swap Meet	23	2nd November 2009 05:04 PM
Big sale thread: PHL, Raven, Amps, In-wall/ceiling speakers, Amps, VideoRequest	mbcouple	Swap Meet	2	27th October 2008 10:27 PM
SMPS for diy audio amps and multi-channel diy amps (and their power supplies)	tlparker	Solid State	18	31st August 2006 10:39 AM
Why do some Bogan amps sound so good as guitar amps?	amperex	Instruments and Amps	7	22nd June 2006 11:46 AM
Has anyone compared GC amps(LM3875/3886/4780) with other DIY SS amps(Leach,ESP) ?	percy	Chip Amps	31	13th January 2006 01:33 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

12th August 2011, 10:54 PM	#281
pre65 diyAudio Member Join Date: Oct 2005 Location: Essex/Suffolk borders.UK	I have a pair of 833a monoblocks. Currently undergoing mods to take them to mk3 version.

13th August 2011, 06:01 AM	#283
pre65 diyAudio Member Join Date: Oct 2005 Location: Essex/Suffolk borders.UK	Actually, it's not that high. I was advised that 1,000V was minimum for good results, but with the PSU bits I had to hand iv'e "only" managed about 950V HT First version used my 300b SET amp via a 5K output transformer on the 16R tap to drive the 833a grid, sounded very nice. Version 1A used a small interstage transformer at about 1 :4.5 ratio, but that was less successful. Current version (mk 2) uses a 6SN7 and EL34 (as cathode follower with fixed negative bias) to drive 833a. Next version will give a negative supply to the EL34 cathode to correct a slight anomaly on the waveform that the scope found. Philip Ramsey (Bluebell Audio) is trying to get Hammond to make some special interstage ( about 6:1 from memory) driving transformers, as he thinks that is the best way. I'm sure going to want to try them when (or if) they become available.