Thanks for the updated PS schematc; most helpful.
For newbies/dummies like me, does anyone have some hi-res pics they could throw up of the underside of the Musical Machine? I'm still learning how to read schematics and transfer the picture on the page into a picture in my mind. It would really help me a lot to see some pics of real life parts/wiring.
Thanks in advance!
For newbies/dummies like me, does anyone have some hi-res pics they could throw up of the underside of the Musical Machine? I'm still learning how to read schematics and transfer the picture on the page into a picture in my mind. It would really help me a lot to see some pics of real life parts/wiring.
Thanks in advance!
Oops.
Anybody who saved that schem, save it again. Hosed the bias circuit resistances, forgot they're in parallel. These values, with the 10K pot, give a very nonfussy adjustment, with 26V at the top of the pot and 20V at the bottom. If that's not enough adjustment for the 6V6s you have, maybe a 15 or 20K pot in there. Old stock 6V6 seem to bias at about -20V for 33-35mA draw; the modern EH and TungSol at about -23V. They require a little more swing on the grid for full modulation, but will deliver a little more power.
Aloha,
Poinz
AT
Anybody who saved that schem, save it again. Hosed the bias circuit resistances, forgot they're in parallel. These values, with the 10K pot, give a very nonfussy adjustment, with 26V at the top of the pot and 20V at the bottom. If that's not enough adjustment for the 6V6s you have, maybe a 15 or 20K pot in there. Old stock 6V6 seem to bias at about -20V for 33-35mA draw; the modern EH and TungSol at about -23V. They require a little more swing on the grid for full modulation, but will deliver a little more power.
Aloha,
Poinz
AT
Poinz,
I always on the lookout for "iron" sources. Who, if anyone, stocks the Tonyaba choke shown?
I always on the lookout for "iron" sources. Who, if anyone, stocks the Tonyaba choke shown?
Thazzrite. Chung has some very good and economical iron. The chokes are gapped so they're not operating in saturation like Hammonds and such, and have a core ground wire.
Constraint with VT4C is that the shipping is a killer. You need to look through the site and stock up on stuff. I like his RCA jacks, silver wire and teflon tubing, the chokes in a couple of values, and chassis knobs. For those of you building in OEM boxes, he has some very robust and economical chassis too. Good guy, very stand-up.
Aloha,
Poinz
AT
Constraint with VT4C is that the shipping is a killer. You need to look through the site and stock up on stuff. I like his RCA jacks, silver wire and teflon tubing, the chokes in a couple of values, and chassis knobs. For those of you building in OEM boxes, he has some very robust and economical chassis too. Good guy, very stand-up.
Aloha,
Poinz
AT
Is the .01uF across the 250VAC Secondary for noise suppression.
Is the 10uF on the 6.3V supply for the same reason? I don't see differential noise being a big issue on filament supplies and common mode (wrt Ground) won't be effected by this cap. Or is there a missing diode and you are creating a DC supply which you drop to 6.3V with the two dropping resistors? In which case, 10uF seems a bit small.
Is the 10uF on the 6.3V supply for the same reason? I don't see differential noise being a big issue on filament supplies and common mode (wrt Ground) won't be effected by this cap. Or is there a missing diode and you are creating a DC supply which you drop to 6.3V with the two dropping resistors? In which case, 10uF seems a bit small.
Evening bump,
Is this a too newb of a question?
Besides the 2 switched pins, and diff OPuts.
Where might I need to be with different voltages for
running 7591 outputs.
Thank you kindly, for any and all help.
Is this a too newb of a question?
Besides the 2 switched pins, and diff OPuts.
Where might I need to be with different voltages for
running 7591 outputs.
Thank you kindly, for any and all help.
The .01μF cap across the transformer side of the diode stack is to shunt the turnoff burst of the diodes, which in UFxxxx types is easily filtered out of causing transformer secondary problems in this way. If you use FRED or Schottky type diodes, this cap may be omitted. Do not use 1Nxxxx type diodes. Noisy stuff.
The 10μF cap across the heater line is there to shunt rubbish coming in on the AC out of the wall. One no longer need live in a heavily industrial area to have very fuzzy power, since all sorts of home stuff uses switching power supplies nowadays. The value of this cap should place its Xc at a hundred times or so of the heater net resistance at 60Hz, to filter the >1Khz nasties out while not absorbing enough mojo from the 60Hz to let the blue smoke out of the capacitor. This cap needs, of course, to be nonpolarized.
Aloha,
Poinz
AudioTropic
The 10μF cap across the heater line is there to shunt rubbish coming in on the AC out of the wall. One no longer need live in a heavily industrial area to have very fuzzy power, since all sorts of home stuff uses switching power supplies nowadays. The value of this cap should place its Xc at a hundred times or so of the heater net resistance at 60Hz, to filter the >1Khz nasties out while not absorbing enough mojo from the 60Hz to let the blue smoke out of the capacitor. This cap needs, of course, to be nonpolarized.
Aloha,
Poinz
AudioTropic
The bias voltage and drive signal requirements for the 7591 are the same as those for the 6V6 and EL84. O/P trafos with a 6.6 KOhm primary are in order. Anode and g2 voltages are not too far removed from those of the EL34. Look at the data sheet.
Wouldn't it be a little safer to take the bias from the top of the pot, not the wiper, and take the wiper to the bottom of the pot? Would need to adjust the resistor either side some.
Sheldon
Thanks Eli, I should'nt have been searching MM,but Instead El Grande. You've given this info several times already.
When I found all that I was reallly impressed with El Cheapo, being that I'm building a MM6v6, the thought of a ECGrande7591, (I have 95% of the parts) with a touch of feedback has got me wondering. Please watch for a thread of this nature from me. Like others I'm good at following direction, but you guys are the brains, i.e. lots of questions.
When I found all that I was reallly impressed with El Cheapo, being that I'm building a MM6v6, the thought of a ECGrande7591, (I have 95% of the parts) with a touch of feedback has got me wondering. Please watch for a thread of this nature from me. Like others I'm good at following direction, but you guys are the brains, i.e. lots of questions.
The bias voltage and drive signal requirements for the 7591 . . .
Eli, you have it exactly. To make a 7591 amp, Golana, just make a 6V6 or EL84 amp with twice the power capability and another hundred volts in the main B+ supply. I seem to remember that the 7591 likes about 400V and 50mA, you'll want to check with the datasheet.
Aloha,
Poinz
AudioTropic
Eli, you have it exactly. To make a 7591 amp, Golana, just make a 6V6 or EL84 amp with twice the power capability and another hundred volts in the main B+ supply. I seem to remember that the 7591 likes about 400V and 50mA, you'll want to check with the datasheet.
Aloha,
Poinz
AudioTropic
Matched 6gk5 & Power Transformer
Hello everyone!
I've been following this thread with great interest and for a few years - yes, years - I've been planning to build a Musical Machine.
I've been looking for sources for the 6GK5 tube and while I've found quite a few, no one is offering matched pairs. Should I look for matched pairs - one matched pair for each channel or is it OK to go with non-matched tubes?
I'd like to go with a single toroidal transformer in the PSU. In the past I've ordered custom wound transformers from www.toroidy.com, not very expensive and shipping costs from Poland to Portugal are fair.
Looking at the specs for the Antek AN-1T250 I can see it is a 100VA transformer with two 250V and two 6.3V @ 3A secondaries.
Lets deal with the heaters supply now, that is ~40VA (2x 6.3V x 3A) but looking at the schematic only one 6.3V secondary is used - green and blue wires.
The 6V6 specs state 0.45A heater current and 0.18A for the 6GK5. With a total of 8 tubes (4 of each) that is 2.52A from a single 3A secondary which doesn't sound too good to me. Should I ask for 4A in my custom wound transformer?
I can't see the current rating of the 250V secondaries, but I'd say 120mA for each if my math is right but from the schematic I can't confirm if both are connected in parallel. Can anyone confirm what should be the ratting of the 250V secondary?
Finally, the Amveco 62035 is rated at 159mA with the two 22V secondaries in series so my custom transformer should have the following specs:
1x 250V @ 240mA
1x 44V @ 160mA
1x 6.3V @ 4A
Is this correct?
Thank you,
Luis
Hello everyone!
I've been following this thread with great interest and for a few years - yes, years - I've been planning to build a Musical Machine.
I've been looking for sources for the 6GK5 tube and while I've found quite a few, no one is offering matched pairs. Should I look for matched pairs - one matched pair for each channel or is it OK to go with non-matched tubes?
I'd like to go with a single toroidal transformer in the PSU. In the past I've ordered custom wound transformers from www.toroidy.com, not very expensive and shipping costs from Poland to Portugal are fair.
Looking at the specs for the Antek AN-1T250 I can see it is a 100VA transformer with two 250V and two 6.3V @ 3A secondaries.
Lets deal with the heaters supply now, that is ~40VA (2x 6.3V x 3A) but looking at the schematic only one 6.3V secondary is used - green and blue wires.
The 6V6 specs state 0.45A heater current and 0.18A for the 6GK5. With a total of 8 tubes (4 of each) that is 2.52A from a single 3A secondary which doesn't sound too good to me. Should I ask for 4A in my custom wound transformer?
I can't see the current rating of the 250V secondaries, but I'd say 120mA for each if my math is right but from the schematic I can't confirm if both are connected in parallel. Can anyone confirm what should be the ratting of the 250V secondary?
Finally, the Amveco 62035 is rated at 159mA with the two 22V secondaries in series so my custom transformer should have the following specs:
1x 250V @ 240mA
1x 44V @ 160mA
1x 6.3V @ 4A
Is this correct?
Thank you,
Luis
Yes, that's all right. The 44V winding can be 50V or 60V; I used a way overspecced 44V Amveco to get an actual 66Vac out of the winding. The 10M45 chip can take 400 volts across it and dissipate 40 watts of power if heatsinked. At 68V and 10mA, it's burning seven tenths of a watt. I'm actually a little worried about operating the chip out the bottom of its published specs.
Ohm's law is your friend, Luis. You got to do some of your own homework.
Best Aloha,
Poinz
Ohm's law is your friend, Luis. You got to do some of your own homework.
Best Aloha,
Poinz
Since the LTP has an active tail load, tube matching really isn't necessary. Furthermore, even if the tubes started out matched, it's highly unlikely they'd stay matched as they age.