Salas, adding a quality transformer to the output to have the option of balanced interconnection. Can i double up on buffer Jfets to decrease Zo or do you think this is an unnecessary step?
I do not pretend to be SALAS but in my experience the phono amp seems to have plenty of drive.
I have used it to power an amp with a 10K input impedance along with one with a 100K input impedance and a crossover with a 60K input impedance and would drive them ALL just fine. Forgot to mention that there is a SLAGLE autoformer attenuator between the phono amp and the amplifiers.
I do intend to use the PASS complimentary buffer after the output and before the autoformer eventually just to hear if it makes any difference.
I would hesitate to double up on anything unless it is absolutely necessary just because I worry about the interactions and in addition I doubt you need the extra current but I have no real idea!
I like transformers and would not hesitate to use them if I had amplifiers with balanced inputs.
Are you going to use a transformer at the amp's input, also, or is it already balanced? Just curious.
I have used it to power an amp with a 10K input impedance along with one with a 100K input impedance and a crossover with a 60K input impedance and would drive them ALL just fine. Forgot to mention that there is a SLAGLE autoformer attenuator between the phono amp and the amplifiers.
I do intend to use the PASS complimentary buffer after the output and before the autoformer eventually just to hear if it makes any difference.
I would hesitate to double up on anything unless it is absolutely necessary just because I worry about the interactions and in addition I doubt you need the extra current but I have no real idea!
I like transformers and would not hesitate to use them if I had amplifiers with balanced inputs.
Are you going to use a transformer at the amp's input, also, or is it already balanced? Just curious.
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I have a balanced/SE preamp and XA amplifier.
If you view the data sheet for most output transformers, the lower the Zo, the better the distortion performance. Doubling jfets would increase Ciss a bit, but not much, and would come close to cutting Zo in half.
If you view the data sheet for most output transformers, the lower the Zo, the better the distortion performance. Doubling jfets would increase Ciss a bit, but not much, and would come close to cutting Zo in half.
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Whose transformer are you thinking about using?
If you have not made a choice yet you should contact Dave Slagle and get something made exactly for your application.
Dave's work sounds good and he is a pleasure to work with.
I have found the LUNDAHLs to be too flexible. Like a diner menu - lots of choices but none them great.
That is the limit of my experience.
If you have not made a choice yet you should contact Dave Slagle and get something made exactly for your application.
Dave's work sounds good and he is a pleasure to work with.
I have found the LUNDAHLs to be too flexible. Like a diner menu - lots of choices but none them great.
That is the limit of my experience.
I wonder if you can use those to convert single ended to balanced?
I am thinking you need a center tap. I wish I knew more about transformers than I do but I think you do. Hoping someone will give the definitive answer later.
If you have them laying about you can always just give it a try!
I am thinking you need a center tap. I wish I knew more about transformers than I do but I think you do. Hoping someone will give the definitive answer later.
If you have them laying about you can always just give it a try!
That's good.
Well, give it a go. I know I would like to hear what you think of what it does.
Well, give it a go. I know I would like to hear what you think of what it does.
FSP has about 50 Ohm source impedance as it is. Is that figure presenting a problem with what you want to do?
Hi,
I have 11 2SK117GR.
Below my measures and assignments.
Is it the right choices ?
IDSS Assignment (Recommendation guide)
2,94
2,97
2,99 Q3x (3-4mA)
3,00 Q3x (3-4mA)
3,15 Q5x (3-4mA)
3,38 Q5x (3-4mA)
3,51 Q2x (3-4mA)
3,87 Q2x (3-4mA)
5,02 Q7 (4-5mA)
5,36 Q7 (4-5mA)
5,60
Thank you
I have 11 2SK117GR.
Below my measures and assignments.
Is it the right choices ?
IDSS Assignment (Recommendation guide)
2,94
2,97
2,99 Q3x (3-4mA)
3,00 Q3x (3-4mA)
3,15 Q5x (3-4mA)
3,38 Q5x (3-4mA)
3,51 Q2x (3-4mA)
3,87 Q2x (3-4mA)
5,02 Q7 (4-5mA)
5,36 Q7 (4-5mA)
5,60
Thank you
Your choices look good. If you will no get a useful rail adjustment range for any practical reason remember that the answer is making R3x higher value if rail max is not enough or making R3x less value if rail min is too much.
Hi Salas,
The components are soldered, i expect the delivery of transformers.
Thank you for the R3x trick.I am quite excited to listen this preamp.
This will be next week, this week i will be near to you, in Greece.
nounouchet
The components are soldered, i expect the delivery of transformers.
Thank you for the R3x trick.I am quite excited to listen this preamp.
This will be next week, this week i will be near to you, in Greece.
nounouchet
Hi Salas,
I don't know why by R3x changed to 11kOhm on one channel, and 9.1kOhm on the other channel worked to get the adjustment necessary to 35v for both channels. TP1-TP2 measures 3.056v/3.077v respectively. I notice some forum members get 3.5v, should I be aiming for a particular voltage or do they just have to be similar/identical?
Thank you for your guidance.
Kind regards,
Vlad
I don't know why by R3x changed to 11kOhm on one channel, and 9.1kOhm on the other channel worked to get the adjustment necessary to 35v for both channels. TP1-TP2 measures 3.056v/3.077v respectively. I notice some forum members get 3.5v, should I be aiming for a particular voltage or do they just have to be similar/identical?
Thank you for your guidance.
Kind regards,
Vlad
Differences in Q3x IDSS on each channel led you to different R3x. I gave 3-4V in the guide so they aim at the middle. They should be similar in any case. Give me another voltage reading now, C3's input side to ground.
Hi Salas,
With V+=44.2V i get Rail+=29V max with VR2x ajustement for both channels.
R3x=9.1K
How i can obtain Rail+ ~ 35V ?
On a channel, after few minutes, Rail+ dropped to 4.9V !
Thanks
nounouchet
With V+=44.2V i get Rail+=29V max with VR2x ajustement for both channels.
R3x=9.1K
How i can obtain Rail+ ~ 35V ?
On a channel, after few minutes, Rail+ dropped to 4.9V !
Thanks
nounouchet
Add 3.3k in series to 9.1k and try again.
Dropped Rail+ to 4.9V is bad. Did it come up again? Check joints. Reminds of just the output MOSFET's (Q6x) Vgs figure is left and tells trouble in the regulator. See if the CCS MOSFET (Q1x) is still getting hot or if there is still Vbe in the BJT (Q4x).
Dropped Rail+ to 4.9V is bad. Did it come up again? Check joints. Reminds of just the output MOSFET's (Q6x) Vgs figure is left and tells trouble in the regulator. See if the CCS MOSFET (Q1x) is still getting hot or if there is still Vbe in the BJT (Q4x).
Hi Salas,
For the good channel with R3x=12,4k, it's ok.
I obtain TP1-TP2=3.6V for Rail+=33.9V and V+=44.4V
I tried (just with my smartphone) and it works.
For the bad channel, i measured:
Rail+=6.2V; V+=53V; Q4x vbe=0.7V; Q6x vgs=0.7V; VR4x=0V;
I have 2 transformers 50VA for the PSU.
Should i change one component ?
Thank you
nounouchet
For the good channel with R3x=12,4k, it's ok.
I obtain TP1-TP2=3.6V for Rail+=33.9V and V+=44.4V
I tried (just with my smartphone) and it works.
For the bad channel, i measured:
Rail+=6.2V; V+=53V; Q4x vbe=0.7V; Q6x vgs=0.7V; VR4x=0V;
I have 2 transformers 50VA for the PSU.
Should i change one component ?
Thank you
nounouchet
Maybe Q6x has a problem. Change that first but Q1x may reveal to have the problem. Couple of builders had found they chanced on one or two dead MOSFETS maybe due to static in the past. In general compare voltage measurements around semiconductors in the regulators between the good and the bad channel so to find the problematic ones.
I changed Q6x and Q1x (they were reversed) but Rail+=4,7V
I changed Q2x but i had i problem with the fuse. I must change it and continue...
I changed Q2x but i had i problem with the fuse. I must change it and continue...