Hi, Earl,
I'm using a home built amp based on a high power Tripath class-D (or, class-T, as Tripath calls it) reference design PCB, which I optimized for driving low load impedances, and also tweaked with a few key passive part substitutions. The amp chassis in which contains two such stereo PCBs (sharing a common power supply), each stereo PCB configured in a mono balanced differential H-bridge topology.
According to the design notes, the amp should produce 200W in to 8 ohms, 350W in to 4 ohms, and 650W in to 2 ohms. I believe that the input sensitivity is 1VRMS, but that's just my recollection. The resulting sound is fabulously transparent. I was quite shocked. Way better sounding than the Audio Research Classic 120 tube monoblocks I had, and therefore sold.
I'm using a home built amp based on a high power Tripath class-D (or, class-T, as Tripath calls it) reference design PCB, which I optimized for driving low load impedances, and also tweaked with a few key passive part substitutions. The amp chassis in which contains two such stereo PCBs (sharing a common power supply), each stereo PCB configured in a mono balanced differential H-bridge topology.
According to the design notes, the amp should produce 200W in to 8 ohms, 350W in to 4 ohms, and 650W in to 2 ohms. I believe that the input sensitivity is 1VRMS, but that's just my recollection. The resulting sound is fabulously transparent. I was quite shocked. Way better sounding than the Audio Research Classic 120 tube monoblocks I had, and therefore sold.
I've also been messing around with one of these for past month or so, it is sounding quite good however, major buzz prolems...tried the removing interface tx and using resistor for I/V conversion but still lots of buzz and flat sound, reduced RL/RR4.. still buzz, increased 120uf on HVPSU to 650uf - still buzz. I notice I have 390vdc at R1 in the SRPP which seems very high, the schematic states 230v the vr pot in the HVPS does not appear to have any impact on voltage level, I'm thinking something probably in PSU is wrong/faulty - there are lots of errors on that schematic, exchanged a few emails with seller but he has gone quiet since last email...considering an aikido with valve ps to replace the srpp section of this board - not sure which version would work best though? maybe with sowter or even vintage partridge 1:6 tx for interace as I'd like to stick with the tx interface concept, I use Partrdige 973 1:16 in my vinyl set-up and they are very good..
That sounds dangerous. What are the measurements for the plate voltage on the 6DJ8 tube? (plate to cathode)
Hi,
I'm afraid I'm new to the world of tubes, although glad I've eventually arrived!! I don't know how to measure what you refer to, i.e I don't phyically know at what point on the board to take that measurement? I'm also concerned that the order of pins on the srpp is not conventional as I have heater 6.3 v reading on pin 4 of left channel tube but on pin 6 of right channel tube, this has confused me and put me off measuring a little, I've got to say though, despite the hum this dac sounds good to me, I was previously using my cambrdige audio 640 cd player straight from wolfson DAC chips as per lampizator 'snip it' mod which was a big imoprvement over standard player but this dac is much beter at everything....except hummmmm!!
Terry
I'm afraid I'm new to the world of tubes, although glad I've eventually arrived!! I don't know how to measure what you refer to, i.e I don't phyically know at what point on the board to take that measurement? I'm also concerned that the order of pins on the srpp is not conventional as I have heater 6.3 v reading on pin 4 of left channel tube but on pin 6 of right channel tube, this has confused me and put me off measuring a little, I've got to say though, despite the hum this dac sounds good to me, I was previously using my cambrdige audio 640 cd player straight from wolfson DAC chips as per lampizator 'snip it' mod which was a big imoprvement over standard player but this dac is much beter at everything....except hummmmm!!
Terry
I have a modified Audionote Dac. It sounds better w/o the transformers (passive I/V with a resistor).
Some interesting notes on connecting a units ground to the chassis (protective earth)
http://www.hottconsultants.com/questions/chassis_to_circuit_ground_connection.html
http://www.hottconsultants.com/questions/chassis_to_circuit_ground_connection.html
Yes, I recall now with my unit I had to connect the signal GND to the chassis GND and the buzz went away. I also took out the transformers, the sound was much better.
Get some E288CC to replace the E88CC, they sound better in SRPP configuration....
Get some E288CC to replace the E88CC, they sound better in SRPP configuration....
I've replaced the transformers with Partridge 977 1:6, buzz has reduced drastically, much better sound in every way than stock tx, they really are rubbish, I hear what everyone is saying about deleting tx full stop, however, I can't find any info on anyone changing them out for beter ones so thought I'd try, as mentioned above I tried with resistor for IV but sounded a bit flat and too similar to what I already had from the Cambdridge CD player.
Now the buzz is gone and things are pretty quiet with volume pot at a 'normal' level, if I crank it up to what would be a really loud listening level - get those drums sounding real level - then there is still some noise, more like a higher pitched hum than previously with the stock tx which was around 100hz, this is also mixed with an irregular crackle type sound similar to white noise. I have noticed that when all ground connections from board to chassis are disconnected (inc stand-offs) so no physical deliberate/obvious connection between pcb and chassis I measure a 10ohm resistance between ground points on pcb and chassis ground?? confused..by this, is it normal?? I would have thought without a deliberate connection between pcb ground and chassis ground the meter should read 1 i.e not conduct between the 2??
Lordearl wth regard to the E288CC does that require any change to srpp circuit i.e resistor values etc or just drop-in? Is it an all round general sort of sounds better or in specific areas?
Cheers Terry
Now the buzz is gone and things are pretty quiet with volume pot at a 'normal' level, if I crank it up to what would be a really loud listening level - get those drums sounding real level - then there is still some noise, more like a higher pitched hum than previously with the stock tx which was around 100hz, this is also mixed with an irregular crackle type sound similar to white noise. I have noticed that when all ground connections from board to chassis are disconnected (inc stand-offs) so no physical deliberate/obvious connection between pcb and chassis I measure a 10ohm resistance between ground points on pcb and chassis ground?? confused..by this, is it normal?? I would have thought without a deliberate connection between pcb ground and chassis ground the meter should read 1 i.e not conduct between the 2??
Lordearl wth regard to the E288CC does that require any change to srpp circuit i.e resistor values etc or just drop-in? Is it an all round general sort of sounds better or in specific areas?
Cheers Terry
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