re: high pitched whistling
try swapping the primaries, it helped me
Q: Trainwreck Express PT Power Transformer Settings
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Re: Q: Trainwreck Express PT Power Transformer Settings
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Re: Q: Trainwreck Express PT Power Transformer Settings
Ok guys, i finished the 2nd Express build for a friend and had no issues on the 1st try even thou i didn't even use a resistor on the 1st triode Pin 7!
I went back to mine and routed the input to the outside of the standoffs as someone pointed out. There was no issue with the transformer wires. The starting and ending winding went to were they need to be and verified in the build guide (blue to V4 and brown to V5 I think). I added a shielded cable on the volume pot to the V1 (as I did on the second amp. i rerouted the NFB to the outside of the standoffs, rerouted the PI wires, and added more windings to the heater wires just in case.
Soo, not sure which one's did it, but all help and end result....working as should and quiet! I played some AC/DC and Ozzy with some soft/hard Deep Purple/Whitesnake stuff. I'm in love! Attached are some photos of he new one awaiting final graphics and enclosure. Enjoy!
p.s. - mine has a 15k resistor on the Pin7 of V1, the second has no attnuation! Both amps are using all JJ tubes with a plate around 400V and biased at ~24.5mA
Robb
I went back to mine and routed the input to the outside of the standoffs as someone pointed out. There was no issue with the transformer wires. The starting and ending winding went to were they need to be and verified in the build guide (blue to V4 and brown to V5 I think). I added a shielded cable on the volume pot to the V1 (as I did on the second amp. i rerouted the NFB to the outside of the standoffs, rerouted the PI wires, and added more windings to the heater wires just in case.
Soo, not sure which one's did it, but all help and end result....working as should and quiet! I played some AC/DC and Ozzy with some soft/hard Deep Purple/Whitesnake stuff. I'm in love! Attached are some photos of he new one awaiting final graphics and enclosure. Enjoy!
p.s. - mine has a 15k resistor on the Pin7 of V1, the second has no attnuation! Both amps are using all JJ tubes with a plate around 400V and biased at ~24.5mA
Robb
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MikeSafreed
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Re: Q: Trainwreck Express PT Power Transformer Settings
Robb,
Nice job. Glad you got it all sorted out.
I think someone pointed out in an earlier post that you might want to rethink how you are using that aluminum power resistor you have mounted on the PS board. That resistor is going to need to dissipate some heat, and the way the aluminum casing accomodates that is to pass the heat to the chassis. Since the resistor is not mounted to the chassis, it will will not effectively get rid of the heat. I would suggest that you consider replacing that resistor with a 1K 25 watt ceramic wire wound, and mount it in the same place, but leave about 1/8" of space under it. It will shed the heat that way. I like those aluminum cased power resistors, but for this amp there's no place to mount it and preserve the original amp layout. Just a suggestion, that might save you a more costly repair down the road...
Again, nice job!
Mike
Nice job. Glad you got it all sorted out.
I think someone pointed out in an earlier post that you might want to rethink how you are using that aluminum power resistor you have mounted on the PS board. That resistor is going to need to dissipate some heat, and the way the aluminum casing accomodates that is to pass the heat to the chassis. Since the resistor is not mounted to the chassis, it will will not effectively get rid of the heat. I would suggest that you consider replacing that resistor with a 1K 25 watt ceramic wire wound, and mount it in the same place, but leave about 1/8" of space under it. It will shed the heat that way. I like those aluminum cased power resistors, but for this amp there's no place to mount it and preserve the original amp layout. Just a suggestion, that might save you a more costly repair down the road...
Again, nice job!
Mike
Mike Safreed - S&S Amplification
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Re: Q: Trainwreck Express PT Power Transformer Settings
Do you have any sound clips? I am curious how those filter caps sound in comparison to the high dollar Mallory caps used in the original Express builds... would be interested to know if there is an audible difference?
rj
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Re: Q: Trainwreck Express PT Power Transformer Settings
sure thing. i'm outof the country all week on business, but i'll post clips this weekend after i get back. i wouldn't waste my money on too high dollar stuff. i use the 5% Cornell Dubilier polyesters on all my amp builds and they sound killer!
Robb
Robb
Re: Q: Trainwreck Express PT Power Transformer Settings
Can't wait to get back home and tweak the amps this weekend! I'm thinking I'll mess around with the input attenuation and maximize signal while ensuring getting rid of any parasitic microphonics....probably 10k to 33k range.
I'm going to throw in pink noise signal into the amp and measure and see how the frequencies respond with the spectrum analyzer. I think my approach will just be to tweak the tone stack and cut the dB's at certain frequency to taste....therefore if the spectrum analyzer shows a spike at 1k, I'll tweak the tone stack to cut 1k without affecting too many frequencies outside of that. The player can determine if they want to leave as-is, or cut back on the frequency(s)!
Generally speaking and looking over and doing some calculations with the Tone Stack calculator, I like how the Fender stack really impacts the frequencies, but there seems to be a lot of loss to overall signal.
To maximize signal and still get a good flat and yet responsive controls, the following looks like a good mix - change R4 from 100k to 33k, R2 from 1M-A to 250k-A and R4 from 250k-B to 100k-B. The signal seems maximized and flat 20-20kHz with the dials at B-10, M-10, T-2 which is where I'd like to be...maximize signal and flat all dials at 10 and attenuate back! With these valuse, bass cut is about 10dB, mid cut is 15dB, and treble is about 3dB w/ reshape of the curve. -17dB at 1kHz.
Since I don't like the bright switch as it's radiculously bright with it on, it'll probably go away, take it out and just use a standard 470pF from VR4P1 to ground.
That's about it for now. I'll post clips this weekend. Maybe should start a different thread as this one was oiginally about transformers! p.s. - the Magnetic components are great and no issues!
Robb
I'm going to throw in pink noise signal into the amp and measure and see how the frequencies respond with the spectrum analyzer. I think my approach will just be to tweak the tone stack and cut the dB's at certain frequency to taste....therefore if the spectrum analyzer shows a spike at 1k, I'll tweak the tone stack to cut 1k without affecting too many frequencies outside of that. The player can determine if they want to leave as-is, or cut back on the frequency(s)!
Generally speaking and looking over and doing some calculations with the Tone Stack calculator, I like how the Fender stack really impacts the frequencies, but there seems to be a lot of loss to overall signal.
To maximize signal and still get a good flat and yet responsive controls, the following looks like a good mix - change R4 from 100k to 33k, R2 from 1M-A to 250k-A and R4 from 250k-B to 100k-B. The signal seems maximized and flat 20-20kHz with the dials at B-10, M-10, T-2 which is where I'd like to be...maximize signal and flat all dials at 10 and attenuate back! With these valuse, bass cut is about 10dB, mid cut is 15dB, and treble is about 3dB w/ reshape of the curve. -17dB at 1kHz.
Since I don't like the bright switch as it's radiculously bright with it on, it'll probably go away, take it out and just use a standard 470pF from VR4P1 to ground.
That's about it for now. I'll post clips this weekend. Maybe should start a different thread as this one was oiginally about transformers! p.s. - the Magnetic components are great and no issues!
Robb