Thank you. I still have some little hum on higher Z headphones, no matter what and how I do so still struggling, went from star earth to bus type, changed plain AC heating to a virtual-centered, gnd-referenced AC, then to full DC, no change. RCA input side doesn't change anything if I lift ground or not ..
The power capacitors are quite old, 2x 470uF / side, maybe I'll swap them to newer ones when I put the amp into another chassis soon.
2 separate B+ lines for L and R, diodes 4x Vishay ultrafast Hexfreds per side, epoxy potted 160VA toroidal transformer with 3 secondaries (1x 6.3V/6A, 2x 200V/0.3A) with some reserve and I still have no clue why the whole thing has this little hum. But I'll find out soon. 🙂
For a choke (calculating..) do we only take voltage swing into consideration or the whole constant current draw (~90% heat) + ~10% (output voltage swing) of the class A circuit ?
The power capacitors are quite old, 2x 470uF / side, maybe I'll swap them to newer ones when I put the amp into another chassis soon.
2 separate B+ lines for L and R, diodes 4x Vishay ultrafast Hexfreds per side, epoxy potted 160VA toroidal transformer with 3 secondaries (1x 6.3V/6A, 2x 200V/0.3A) with some reserve and I still have no clue why the whole thing has this little hum. But I'll find out soon. 🙂
For a choke (calculating..) do we only take voltage swing into consideration or the whole constant current draw (~90% heat) + ~10% (output voltage swing) of the class A circuit ?
Hi again and many-many thanks for your patience here with me 🙂
I'm back and now just looking for these chokes + new chassis for the project, no more space and it was crowded already anyway.
Jus tto finalize figures, you wrote the stereo pair takes about 50mA while the circuit swings approx. 20mA.
For 1 circuit (mono), is it then approx. 25mA idle current draw and about 45mA at max ? (25 + 20).
My setup is dual-mono, only the transformer's primary winding is a common one.
I have 2 secondaries -> 2 diode bridges -> 2 smoothing cap blocks, so 2 independent PSU-s for the L and R side circuits actually.
Need to calculate choke also for 1 side (and buy 2 chokes then). 🙂
I'm back and now just looking for these chokes + new chassis for the project, no more space and it was crowded already anyway.
Jus tto finalize figures, you wrote the stereo pair takes about 50mA while the circuit swings approx. 20mA.
For 1 circuit (mono), is it then approx. 25mA idle current draw and about 45mA at max ? (25 + 20).
My setup is dual-mono, only the transformer's primary winding is a common one.
I have 2 secondaries -> 2 diode bridges -> 2 smoothing cap blocks, so 2 independent PSU-s for the L and R side circuits actually.
Need to calculate choke also for 1 side (and buy 2 chokes then). 🙂
Hi gentlemen,
I'm finally putting together all the stuff.. not an easy task while working and having a girlfriend too 🙂
Anyway, I have some spare time now and I thought I finish my little OTL of Tim Mellow.
Question1:
In the original article, there's 1 PSU shown, feeding both Left and Right side circuits, right ?
I think schematics is for mono circuit (of course) but the PSU was meant for driving both sides (stereo).
T1 is specified for 15VA ->
I might be in trouble with my transformers. Or even not - can you elaborate the 'issue' if there's any, please ?
To whatever reason, I ordered 4 transformers for this project 3-4 years ago:
T1 (25VA - more than needed)
T2 (250VA - more than needed)
2x T3 (400VA each - less than original but I have 2 of these then, this way more capacity again)
The idea was to have heaters for both sides on common secondaries as in the original article (I assume), but for the anode voltages let's use 2 separate transformers and full circuits behind them.
So far nice, but now comes the trick and my question
Thinking in stereo integrated constellation:
- all 4 driver tubes' heater potential needs to be pushed down to -450V (HT3).
and I have 2 HT4-s, again for Left and Right side.
Which HT3 and HT4 points shall I use for these common fed heaters ? Left or right ? Can I do it at all without screwing up something ? (E.g. using Left side's HT3 for all affected heatings and Right side's HT4 for all affected heatings).
I'm finally putting together all the stuff.. not an easy task while working and having a girlfriend too 🙂
Anyway, I have some spare time now and I thought I finish my little OTL of Tim Mellow.
Question1:
In the original article, there's 1 PSU shown, feeding both Left and Right side circuits, right ?
I think schematics is for mono circuit (of course) but the PSU was meant for driving both sides (stereo).
T1 is specified for 15VA ->
for stereo when feeding 2 input tubes (2x 0.37A) and 4 driver tubes (4x 0.22A) altogether, current draw is 0.74 + 0.88 = 1.62A (~10.2VA) so we're still good
T2 is specified for 225VA -> for stereo when feeding 4x 6C33C tubes (4x 3.6A 12Vseries connected), current draw is 14.4A -> ~172 VA so this is again ok
T3 is specified for 625VAfor stereo I assume one side only needs half of this approximately (or even less)
Question2: I might be in trouble with my transformers. Or even not - can you elaborate the 'issue' if there's any, please ?
To whatever reason, I ordered 4 transformers for this project 3-4 years ago:
T1 (25VA - more than needed)
T2 (250VA - more than needed)
2x T3 (400VA each - less than original but I have 2 of these then, this way more capacity again)
The idea was to have heaters for both sides on common secondaries as in the original article (I assume), but for the anode voltages let's use 2 separate transformers and full circuits behind them.
So far nice, but now comes the trick and my question
Thinking in stereo integrated constellation:
- all 4 driver tubes' heater potential needs to be pushed down to -450V (HT3).
and I have 2 HT3-s, one for Left and one for Right side.
- 2 (of 4) 6S33S' heater potential needs to be pushed down to -150V (HT4). and I have 2 HT4-s, again for Left and Right side.
Which HT3 and HT4 points shall I use for these common fed heaters ? Left or right ? Can I do it at all without screwing up something ? (E.g. using Left side's HT3 for all affected heatings and Right side's HT4 for all affected heatings).
4x 6C33C for basic dynamic 250 Ohm headphones?
That is probably the most crazy idea I've ever heard.
That is probably the most crazy idea I've ever heard.
Member
Joined 2009
Paid Member
I'd love to build some crazy stuff but these days the wired-headphone is getting to be a rare bird.
Hi, About the best sound H/P amp & pre amp you can get is the Pass B1-Korg.
With your current phones all you would need to do is but a buffer at the output stage to the phone. Toggle switch one side to phone, the second side to Pre. This pre has been tested against a $20,000 pre & held it's own.
Quite often comes up on market place for between $200 & $400
Cheers
With your current phones all you would need to do is but a buffer at the output stage to the phone. Toggle switch one side to phone, the second side to Pre. This pre has been tested against a $20,000 pre & held it's own.
Quite often comes up on market place for between $200 & $400
Cheers
No idea what you mean, in the Pass unit it is WORLD class & has no problem driving my Hypex amps.
Cheers
Cheers
Here’s the schematic. https://guides.diyaudio.com/Guide/B1+with+Korg+Nutube/12
The Korg tube draws microamps and is very sensitive to loading.
The Korg tube draws microamps and is very sensitive to loading.
Well, That does not seem to be a problem for the many B1-Korg people who are using it through a suitable buffer.
Cheers
Cheers