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.
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.
hey-Hey!!!,
The choke choice depends on what it is doing. In between two caps as the inductor in a Pi filter is a lot different from input service in an L-C filter.
cheers,
Douglas
The choke choice depends on what it is doing. In between two caps as the inductor in a Pi filter is a lot different from input service in an L-C filter.
cheers,
Douglas
Hi, from the schematic, it does actually sit between two capacitor. The tube rectifier is followed directly by a capacitor, then the choke, and then it goes straight to the OPTX, then after that, there are about 4 more capacitors. So not sure it is function as a PI filter, given there isn't a capacitor between the choke and the OPTX. (See schematic on the site).
Reducing the value on the choke in PSU Designer seems to make the initial ripple peak less than having it a higher value.
Reducing the value on the choke in PSU Designer seems to make the initial ripple peak less than having it a higher value.
It's going alright thanks, just about to place the order for the output transformers, the Edcor CXPP60-8-6.6K . The chokes are going to be open frame Hammond's 159P 10H/125mA, and the power supply from DIY Club, which is a 380V-0-380V unit.
Will get around to posting the pictures some time (already taken some...)
Will get around to posting the pictures some time (already taken some...)
want to see pics 😀
still looking around for the output transformers.. 2 pices of Edcor CXPP60-8-6.6K cost around 220 euro with shipment to denmark.. maybe there are some better choices...
sorry about the bad english
still looking around for the output transformers.. 2 pices of Edcor CXPP60-8-6.6K cost around 220 euro with shipment to denmark.. maybe there are some better choices...
sorry about the bad english
I have built the boards too...
I found 2 irritating issues...the sockets mounts on the "underside", and there are no adjustable bias-circuit.
I still have not planned what trafos to use...
Arne K
I found 2 irritating issues...the sockets mounts on the "underside", and there are no adjustable bias-circuit.
I still have not planned what trafos to use...
Arne K
The Edcor are expensive once you add the postage, but any transformer will be, they are heavy... Have you tried Lundahl? LL1620 seems to be reasonably suitable? Perhaps they could do a custom one that would be cheaper overall? Just a thought...
Here are some photos.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I am still missing two resistors, and will have that soldered soon. The Output transformers and chokes have been ordered, and awaiting their arrival! Still looking for a good value power transformer. Anyone know of one that is suitable?
Hi eeyore
Do you have part list for this circuit with digikey or mousar part numbers ? The list is not there on pmillett's website.
thanks
Do you have part list for this circuit with digikey or mousar part numbers ? The list is not there on pmillett's website.
thanks
Hi beetel,
I don't have one consolidated lists. The parts I used were:
- NOS Allen Bradley Resistors from eBay.
- Kiwame Power resistors (5W+) from DIY Hifi Supply
- Solen SM Tin Foil Coupling Capacitors from Parts Connexion
- Elna Cerafine cathode caps from Welborne Labs
- Sowter phase splitter from Sowter
- The power supply filter caps from Digikey
- KT88 Tubes from Tube Depot
- 12SN7 (change from 6SN7) and 5U4G from AES
I don't have one consolidated lists. The parts I used were:
- NOS Allen Bradley Resistors from eBay.
- Kiwame Power resistors (5W+) from DIY Hifi Supply
- Solen SM Tin Foil Coupling Capacitors from Parts Connexion
- Elna Cerafine cathode caps from Welborne Labs
- Sowter phase splitter from Sowter
- The power supply filter caps from Digikey
- KT88 Tubes from Tube Depot
- 12SN7 (change from 6SN7) and 5U4G from AES
Anyone know where one can find a cheap (<US$50) power transformer with 230/240V primary that is suitable for the Uniamp?
Hey eeyore, I see you've been registered on diyaudio.com for nearly 2 years and you live in Melbourne. I like you DIY efforts on your blog. You should consider joining the Melbourne Audio Club http://home.vicnet.net.au/~macinc/ . It has a circle of DIY audio devotees with a broad range of interests and skills and we have monthly workshops and home meetings for DIY (aka Audio Action).
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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 . 😡
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 . 😡
Hi Eeyore,
Have you tried EVATCO? (www.evatco.com.au).
I bought a choke and an interstage xformer from them.
Both are Hammond products. The xformer does not impress me, though. I think they also stock power xformers.
Have fun.
Serge
Have you tried EVATCO? (www.evatco.com.au).
I bought a choke and an interstage xformer from them.
Both are Hammond products. The xformer does not impress me, though. I think they also stock power xformers.
Have fun.
Serge
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