Akita said:
Actually, I have two of them 🙂 Dual mono...
I had a couple of transformers taken from old tape recorders, so I thougt, why not dual mono 😉
They are mounted inside the chassi:
An externally hosted image should be here but it was not working when we last tested it.
Oh, by the way. My RH84 doesn't have the rh84 power supply.
My power supply uses semiconductor diodes, instead of the tube reflictor...
My power supply uses semiconductor diodes, instead of the tube reflictor...
ollebolle,
I am looking at a RH84 build and interested in possibly using solid state PS as well. Could you possibly give details of your PS - voltages, circuit etc., I see 2 switches - some sort of standby?
Much appreciated, Chris
I am looking at a RH84 build and interested in possibly using solid state PS as well. Could you possibly give details of your PS - voltages, circuit etc., I see 2 switches - some sort of standby?
Much appreciated, Chris
Anothe RH84 up and running
Completed my RH84 in the weekend, sounding good, Initially after voltage checks I hooked up to some speakers - it was SO quiet I though it wasn't working! This thing has no hum or hiss even with my 96db Fostex 208s - I paid a lot of attention to layout, keeping input wiring short and away from power supply. This is the quietest amp I have ever heard.
Power supply using FRED diodes rather than tube rectifier, tubes are Electro Harmonix and Brimar. Power and output transformers are Edcor
Couple of questions:
The B+ comes up at 281V, is there any value in tweaking the dropper resistors in the power supply to get closer to 300?
Power transformer gets fairly warm, is this unusual? Its 250-0-250v @ 250ma, 6.3v @ 4A should be plenty.
Thanks to Alex for a great design.
Cheers
Completed my RH84 in the weekend, sounding good, Initially after voltage checks I hooked up to some speakers - it was SO quiet I though it wasn't working! This thing has no hum or hiss even with my 96db Fostex 208s - I paid a lot of attention to layout, keeping input wiring short and away from power supply. This is the quietest amp I have ever heard.
Power supply using FRED diodes rather than tube rectifier, tubes are Electro Harmonix and Brimar. Power and output transformers are Edcor
Couple of questions:
The B+ comes up at 281V, is there any value in tweaking the dropper resistors in the power supply to get closer to 300?
Power transformer gets fairly warm, is this unusual? Its 250-0-250v @ 250ma, 6.3v @ 4A should be plenty.
Thanks to Alex for a great design.
Cheers
Attachments
ChrisMmm,
Thank you for sharing! It looks cozy inside. Did you build it as it is in the schematic? Also, perhaps you can post more impressions on the sonics when you and your amp get time.
I have some little Tannoy's that would probably do well with this design. I was looking for a simple little el84 single ended amp that I could build 4 of for biamping monoblocks. Might still be a fitting candidate....
cheers.
Mike.
Thank you for sharing! It looks cozy inside. Did you build it as it is in the schematic? Also, perhaps you can post more impressions on the sonics when you and your amp get time.
I have some little Tannoy's that would probably do well with this design. I was looking for a simple little el84 single ended amp that I could build 4 of for biamping monoblocks. Might still be a fitting candidate....
cheers.
Mike.
Yes, other than trhe power supply followed the RH84 circuit exactly.
I initially tried them with some very old Celestion "C" speakers, much less efficient than the Fostex, still got plenty of clean sound from them.
I have been using T-amps for a couple of years, my latest one is capable of some 25watts. The RH drives the Fostex easily as loud. The bass with the RH seems fuller - have yet to decide if its as tight. Both amps have a very clean, dynamic, airy sound. Cost wise they are about the same and I prefer both to the 100watt Plinius amps I had, paired with the Fostex any way.
I initially tried them with some very old Celestion "C" speakers, much less efficient than the Fostex, still got plenty of clean sound from them.
I have been using T-amps for a couple of years, my latest one is capable of some 25watts. The RH drives the Fostex easily as loud. The bass with the RH seems fuller - have yet to decide if its as tight. Both amps have a very clean, dynamic, airy sound. Cost wise they are about the same and I prefer both to the 100watt Plinius amps I had, paired with the Fostex any way.
Hi Sheldon,
Nice job !
I still listen to my RH84 daily, best single ended amp I build so far.
With regards to the heat in your powertranny,
I had simular problems until I tried Yeo's Da Block;
http://diyparadise.com/dablok.html
works like a charm !
I see you haven't got much space inside your amp but
you could always make a dedicated powersocket with
this DC-blocker installed (as I did....)
Cheers,
Empee
Nice job !
I still listen to my RH84 daily, best single ended amp I build so far.
With regards to the heat in your powertranny,
I had simular problems until I tried Yeo's Da Block;
http://diyparadise.com/dablok.html
works like a charm !
I see you haven't got much space inside your amp but
you could always make a dedicated powersocket with
this DC-blocker installed (as I did....)
Cheers,
Empee
B+ voltage
Hi,
Just made a second RH84 for a friend, again working perfectly first time!
Except - we are using a tube rectifier as per original circuit diagram this time and getting a B+ of 328V after it is full warmed up. I can add an RC filter after the LC filter to drop the voltage - do I need to? Is 328V going to damage the tubes?
Thanks.
Hi,
Just made a second RH84 for a friend, again working perfectly first time!
Except - we are using a tube rectifier as per original circuit diagram this time and getting a B+ of 328V after it is full warmed up. I can add an RC filter after the LC filter to drop the voltage - do I need to? Is 328V going to damage the tubes?
Thanks.
Yes, you need to drop it to 300v, or a bit less 298v.
If your B+ is not regulated, it might shot up 10% more to around 360v when the incoming voltage fluctuation happen. For 328v to 360v, I think your el84 may not like it very much.
If your B+ is not regulated, it might shot up 10% more to around 360v when the incoming voltage fluctuation happen. For 328v to 360v, I think your el84 may not like it very much.
Re: B+ voltage
If you are using a 5U4, you can try a 5R4 or a 5Y3. The R4 will reduce the voltage by 15-20V, the Y3, a little more.
Sheldon
ChrisMmm said:
If you are using a 5U4, you can try a 5R4 or a 5Y3. The R4 will reduce the voltage by 15-20V, the Y3, a little more.
Sheldon
Thanks guys.
Yes, using a 5UG so I will have a go with a different rectifier tube - see how that goes.
I realise now that the choke in the RH84 schematic is 20H/50ma (and I still don't understand why he had 50ma when the curcuit will pull around 100ma) but we used 15H/100ma. Its DCR is 256ohm whereas I imagine the 20H/50ma one would be twice that.
Cheers
Yes, using a 5UG so I will have a go with a different rectifier tube - see how that goes.
I realise now that the choke in the RH84 schematic is 20H/50ma (and I still don't understand why he had 50ma when the curcuit will pull around 100ma) but we used 15H/100ma. Its DCR is 256ohm whereas I imagine the 20H/50ma one would be twice that.
Cheers
ChrisMmm said:
It also depends on the DCR of the power transformer. You can plug the primary and secondary DCR, and the unloaded voltage into PSUD. With that and your choke DCR, you can get a very accurate simulation of the B+ with the program.
Sheldon
I let PSUD decide the trafo DCR as it wasn't specified. OTOH can I just put a meter across the secondary to get DCR?
Knowing the load is important too - I estimated based on 40ma x 2 for the EL84 and 10ma for the 12at7. I worked on 100ma.
Seems using a tube rectifier the voltage drop can vary by 20 volts or so.
That aside its a great tool.
Knowing the load is important too - I estimated based on 40ma x 2 for the EL84 and 10ma for the 12at7. I worked on 100ma.
Seems using a tube rectifier the voltage drop can vary by 20 volts or so.
That aside its a great tool.
- Status
- Not open for further replies.