2nd Gen Build

[martin manning]

I would assume it was the timbre that HAD was chasing after as you don't hear comments from people playing or owning authentic 2nd Gen and 3rd Gen amps that they are noisy.

That or it doesn't really matter ;^) Can't hurt, tho.

[dbharris]

I would assume it was the timbre that HAD was chasing after as you don't hear comments from people playing or owning authentic 2nd Gen and 3rd Gen amps that they are noisy.

That or it doesn't really matter ;^) Can't hurt, tho.

Indeed. People much smarter than me and with more amp experience will reach many different conclusions. But I think it is safe to assume that HAD was intentionally orienting the caps in furtherance of some benefit that he perceived, no?

-Dan

[martin manning]

Could be, but who knows? The cap orientation thing was/is an established practice in RF work.

[Dr d]

Thanks for all of the wire suggestions, I have favorited those for the next time I place an order. Been slow going on the amp while I am swamped at work. But wanted to post a little progress.

Main board
PXL_20240225_223816850~2.jpg
PXL_20240225_223900191.jpg

Power board
PXL_20240225_223629068.MP.jpg
PXL_20240225_223651130.jpg


FET (trying a J201 for this build)
PXL_20240225_223949465.jpg
PXL_20240225_224014672.jpg

Hopefully will have more time this week.

-Dan

Hi Dan, I notice that all of your coupling caps shields are orientated toward the pots. Do tell why?

Hi Dr. D,

If you look at the photos in the 2nd Gen Layout thread, that is how HAD did it. In the 3rd Gen amps, I believe all but one of the caps were also oriented that way (maybe bass, but I am going off memory). I've seen many statements to the effect that coupling cap orientation only changes the noise floor, while others say it is one the many ways HAD would manipulate the timbre of an amp. I would assume it was the timbre that HAD was chasing after as you don't hear comments from people playing or owning authentic 2nd Gen and 3rd Gen amps that they are noisy.

I am interested to hear what this one will sound like...

-Dan

Hi Dan, thanks for your response. I remember reading this and, as you say, the photos confirm what you say. I have oriented the caps as HAD did and there is definitely no issue with noise, so I guess he was wanting to scoop the mids. My suggestion, if I may, at this point would be to try to be as accurate as you can in replicating #40. It definitely has its own sound which takes a little while to get used to. Be patient and you will fall in love with this amp, I promise you!

[dbharris]

Hi Dan, I notice that all of your coupling caps shields are orientated toward the pots. Do tell why?

Hi Dr. D,

If you look at the photos in the 2nd Gen Layout thread, that is how HAD did it. In the 3rd Gen amps, I believe all but one of the caps were also oriented that way (maybe bass, but I am going off memory). I've seen many statements to the effect that coupling cap orientation only changes the noise floor, while others say it is one the many ways HAD would manipulate the timbre of an amp. I would assume it was the timbre that HAD was chasing after as you don't hear comments from people playing or owning authentic 2nd Gen and 3rd Gen amps that they are noisy.

I am interested to hear what this one will sound like...

-Dan

Hi Dan, thanks for your response. I remember reading this and, as you say, the photos confirm what you say. I have oriented the caps as HAD did and there is definitely no issue with noise, so I guess he was wanting to scoop the mids. My suggestion, if I may, at this point would be to try to be as accurate as you can in replicating #40. It definitely has its own sound which takes a little while to get used to. Be patient and you will fall in love with this amp, I promise you!

Very good advice and definitely what I am going for. Your build is really incredible!

I also just noticed I tied the V1b and V2b grid resistors to the cathode pins by mistake I'll get that fixed up next time I heat up the iron.

-Dan

[dbharris]

Finished up all of the wiring before adding iron and boards.

PXL_20240330_203940665.jpg

PXL_20240330_204008224.jpg

Choke is from a 1966 Bassman, measuring 95.5 ohms resistance and 3.193H inductance. Also bought a peak atlas LCR meter. Way more accurate on capacitance than my meters and none of mine could do inductance/impedance anyways.

PXL_20240330_204055215.jpg

PXL_20240330_204109262.jpg

There was a slight difference in the inductance depending on which lead was connected to red or back probes. It made me think of Ian and Stephen and others comments that the "direction" of the choke will change the sound/response of an amp (I understand many don't agree with that as well). The measured difference was 3.188H vs 3.193H at 1Khz. The inductance would start higher and settle down to those repeatedly depending on how the leads were connected. Small difference, but it is there. Whether it is perceivable or even if that is what is causing a perceived tonal difference...I do not know.

I still need test the OT for turns ratio, etc. should I measure L anywhere while I am at it?

-Dan

[dbharris]

More Iron:

1973 Fender Bassman PT

PXL_20240331_135125327.jpg

PXL_20240331_135141280.jpg

1967 Fender Bassman OT

PXL_20240331_135014591.MP.jpg

PXL_20240331_135026775.jpg

-Dan

[Dr d]

Finished up all of the wiring before adding iron and boards.

PXL_20240330_203940665.jpg
PXL_20240330_204008224.jpg

Choke is from a 1966 Bassman, measuring 95.5 ohms resistance and 3.193H inductance. Also bought a peak atlas LCR meter. Way more accurate on capacitance than my meters and none of mine could do inductance/impedance anyways.

PXL_20240330_204055215.jpg
PXL_20240330_204109262.jpg

There was a slight difference in the inductance depending on which lead was connected to red or back probes. It made me think of Ian and Stephen and others comments that the "direction" of the choke will change the sound/response of an amp (I understand many don't agree with that as well). The measured difference was 3.188H vs 3.193H at 1Khz. The inductance would start higher and settle down to those repeatedly depending on how the leads were connected. Small difference, but it is there. Whether it is perceivable or even if that is what is causing a perceived tonal difference...I do not know.

I still need test the OT for turns ratio, etc. should I measure L anywhere while I am at it?

-Dan

The choke orientation is definitely significant. Those who can't tell the difference must be hard of hearing!
Nice iron you have there!

[dbharris]

Finished up all of the wiring before adding iron and boards.

PXL_20240330_203940665.jpg
PXL_20240330_204008224.jpg

Choke is from a 1966 Bassman, measuring 95.5 ohms resistance and 3.193H inductance. Also bought a peak atlas LCR meter. Way more accurate on capacitance than my meters and none of mine could do inductance/impedance anyways.

PXL_20240330_204055215.jpg
PXL_20240330_204109262.jpg

There was a slight difference in the inductance depending on which lead was connected to red or back probes. It made me think of Ian and Stephen and others comments that the "direction" of the choke will change the sound/response of an amp (I understand many don't agree with that as well). The measured difference was 3.188H vs 3.193H at 1Khz. The inductance would start higher and settle down to those repeatedly depending on how the leads were connected. Small difference, but it is there. Whether it is perceivable or even if that is what is causing a perceived tonal difference...I do not know.

I still need test the OT for turns ratio, etc. should I measure L anywhere while I am at it?

-Dan

The choke orientation is definitely significant. Those who can't tell the difference must be hard of hearing!
Nice iron you have there!

I am planning to test it out on this amp and also my 102. I need pull that chassis and rebalance the PI now that I have a new quad of power tubes.

Excited to see (hear) these results.

-Dan

[dbharris]

A bit more progress, all iron mounted and most of the power amp wired up. I put a little ring of shrink tube on one lead of the choke to keep it straight when swapping later.

PXL_20240408_164302364.jpg

PXL_20240408_164333905.jpg

-Dan

[Dr d]

Hi Dan, its all looking fantastic and coming together quickly. Btw, how have you grounded your output jacks? I ended up grounding the loop on the pots grounding bar and the output jacks to a ground lug next V4. Hope that helps in some way.
ATB

[dbharris]

Hi Dan, its all looking fantastic and coming together quickly. Btw, how have you grounded your output jacks? I ended up grounding the loop on the pots grounding bar and the output jacks to a ground lug next V4. Hope that helps in some way.
ATB

Good eyes! I had not really decided where to ground it and hadn't considered moving the loop ground to the bus bar. I think I will do just that! In prior builds I relied on one of the output jacks keeping a good connection to the chassis.

As a side note, I may disconnect all of the jacks from the chassis temporarily and use a drill but to chase out the holes. I think perhaps with metric vs imperial they are all a bit snug and I was not positive the isolation washers are keeping things isolated. I am going to do some continuity tests and go from there. I should have gone down that road about a month ago lol.

My head cab arrives today, so now I have more incentive to wrap up the build.

-Dan