Peter Millett's Uniamp with KT88

[Bandersnatch]

Almost. The chassis completed, all the components wired in. BUT having one problem. The transformer also always blows out a fuse when I switch it on. Had some discussions with Pete, and he seems to think that my custom wound Edcor may be wound for a 110V rather than 230V as I specified. Difficult to test without a variac. Am going to connect the two of them back to back, via a heater winding, and see what the voltages are. Unless there is a better way. It blows the fuse unconnected, and fully connected. VERY annoying .

yes, there is a better way! run the power TX up on a variac. If you get proper voltage on the secondary at half the line voltage, you'll know the answer.
cheers,
Douglas

 

[mhouston]

Just about to finish building the PCB version of Pete's Uniamp amp. I am currently selected some OPTX. Don't want to spend too much money, and came across these from Edcor CXPP60-8-6.6K 60 watt push-pull tube amplifier output transformer 6,600 ohms to 8 ohms. Anyone have opinions about the transformer/combination?

Finally, I am also trying to decide on a choke. There are cheap options for a 15H/100mA choke which seems nice, or a similar priced 3H/250mA choke. From simulations (PSU Designer) the average current through the choke is about 90mA, so I guess the 15H/100mA would be out. But would the 3H be too little? Or alternatively, are the suppliers out there with chokes in the 10H/150mA or higher range for around US$15. The other two chokes are at US$10 each.

I have a pair of monoblocks based on the uniamp cct./ brd. and are extremely pleased with them. I have run KT88s (my favourite), 6L6s and EL34s.

 

[lawbadman]

Hello,

For those of you who have built the Uniamp how is it running?

I am thinking of building the Uniamp but I need some feedback at to how it sounds.
I really want to know is how it performs against other tube amps, just to be sure I am making the right decision in building it.




Thanks

Lawrence

 

[mhouston]

Hello,

For those of you who have built the Uniamp how is it running?

I am thinking of building the Uniamp but I need some feedback at to how it sounds.
I really want to know is how it performs against other tube amps, just to be sure I am making the right decision in building it.




Thanks

Lawrence

As I said I have an amp based on this broad. I am extremely pleased with it and the extra bones is tube swapping KT88, EL34 and 6L6. I have all three and swapped them out when the mode takes me. And I can run them in Pentode or triode mode - double bonus! I used Golden Dragon 6SN7s but plain Sovteks and Elecrto-harmonix tubes.

I am a member of the Melbourne Audio Club the second oldest audio club in the world and are DIY convener. I have had dozens of members at my home listening to the uniamp mixed with different preamps (valve and two different SS types), many, many different speakers, cables and music from vinyl and CD.

I am yet to hear ONE member say anything other than "those amps are a bargain" or "you would have to be pretty pleased with the amps". Mine are monoblocked. They can drive anything, run dead quiet and mine weight 27kg each.

Of course the power and output trannies you chose will define the final sound. Get the best you can afford. Both of mine were custom wound locally in Australia and are 3 X oversize. You will be pleased with their incredibly musical performance.

http://diyaudioprojects.com/Gallery/displayimage.php?pos=-116

 

[udailey]

Hey Mark,
Its Uriah. Wondering if this is still a favorite or if you have found further Nirvana in something new?
Uriah

 

[mr2racer]

Can anyone tell me what kind of B+ and current you end up with on the 6SN7's in the front end. I'm building a 2A3 version and have to adjust the power supply?

 

[daniloba]

Some questions for the technicians. Whith adeguate power trasformer might be possible use of KT120 or KT150 tubes on the uniamp pcb? And in case, wich components would be necessary to change?

Thank
Danilo

 

[mr2racer]

I've built two uniamp amplifiers. The first driving a pair of 2A3's and the second EML AD1's. The 2A3 sounded great, the AD1 not so much. I don't think you would have a problem driving either of those tubes. I'm not an expert but I think that front end could drive just about anything.