Master Brightness Caps in Non-HRM Amps

[67plexi]

I'm with Paul on the resistors. The dales' of old sound nothing like the new dale RN65's
Big fan of Mepco-Electra MF7C and IRC 1% resistors and Piher 5% resistors.
The sad part is it's a witch hunt to obtain the resistors from the 1970's
This photo is my take on #124 in its original form except the PPS.
Every one that has played this amp wants to buy it.

Steve.

[ToneMerc]

There have been a lot of comments over the years that HAD used whatever he had to hand, but I really believe that he probably didn't do anything unintentionally.

I spend a fair amount of time studying each amp and the component brand/type. There are some locations where he has tendencies to use whatever he has on hand. However, if you study them enough you will see commonalities and from this you will see patterns. Personally, I follow HAD lead on component choices and try to use equivalent types.

I will repeat this again, the key to these amps is the small things, not the obvious stiff that folks instantly gravitate to.


FWIW, HAD is building his new stuff with what he can commonly find and it appears he's a fan of F&T lytics.

TM

[ToneMerc]

I'm with Paul on the resistors. The dales' of old sound nothing like the new dale RN65's
Big fan of Mepco-Electra MF7C and IRC 1% resistors and Piher 5% resistors.

Yes, definitely resistors do matter.

TM

[stelligan]

Badass builds guys

[talbany]

I think I use Vishay/Dale in all my amps.... are those Xicon? If so, I didn't know that.

Gil
Sorry I meant the brown Dales not Xicons..The CTS pot's also have a way of eliminating some of the harshness and yet seem to stay fairly articulate (could be the carbon trace element)..Ceramic bright caps (vrs Micas) can also help with a harsh OD..Certain component (compositions) have a way IMO of articulating those harsh upper frequencies,those include Pot's ,caps, cabling,resistors, and preamp tubes!!..IMO the simpler the design the more critical these components become..

Good Luck
Tony

[dobbhill]

I have an amp built for me by Henry (Red Plate) that has no brite cap on the master. I took it off. I don't use the brite switch. There is one brite cap in my d'lator, but I can't remember which pot or value.. I'll look if ya want me to. I play Tele's most of the time, but I do have a PRS SE and a Jackson with JB/Jazz pickups. Maybe it's the speakers I use that don't require the brite: Altec 417C's, a reconed JBL D120 (paper dust cap), or a JBL G125. The brite caps just seem to mess everything up to me. No, I don't get Blackface Super-like clean tones, but that's not what this amp is for. I have a Fender for that. My Marshall does that, too, but the D-clone doesn't seem to be missing anything to me.
Just my 2cents...
D

[Structo]

Gil
Sorry I meant the brown Dales not Xicons..The CTS pot's also have a way of eliminating some of the harshness and yet seem to stay fairly articulate (could be the carbon trace element)..Ceramic bright caps (vrs Micas) can also help with a harsh OD..
Good Luck
Tony

I guess I always thought that the silver micas were supposed to be smoother than ceramics.

Maybe I should re-think my use of the micas that I have in my amps.

[Guitarman18]

Tom wrote:

Hi Paul,

What resistors do you like for preamp plates?
Cathodes?
Presence?

Hi Tom,

I kept my Dale RN65's on pre amp plates, even though I bought the vintage MF7C's.. I found the 7C's a bit stiffer and trickier to play (I need all the help I can get!) I did't try KOA's.
On the cathodes I tried Xicon MF, KOA MF, but settled on the MF6c Electra's. They gave clarity and articulation but without brittleness.

My slope resistor is 150K carbon film Beyschlag. Big change over the Xicon CF that used to occupy that slot.
I have Piher on the preamp grids and NFB.
I haven't got hold of correct values to try PI plates or Presence resistor yet.

ToneMerc's builds were my inspiration for looking into resistor changes, but unfortunately I now find myself trawling through ebay on an almost daily basis looking for vintage resistors! I should probably seek help!
Even though I have replaced most of the resistors in my amp, if I couldn't hear the difference between old and new, I went back to what I had originally. So, I'm not just using vintage for the sake of it.

The big dilemma in 102 for me is the mid cap. I have tried everything I can get my hands on and settled on a Phillips cap I believe.

Cheers,

Paul.

[Structo]

Thanks Paul!

[David Root]

Very timely thread for me. I have been trying to figure out how to tweak my #102 to get rid of the OD hash.

Bearing in mind that the amp is not yet broken in, not enough hours on it by far, I am now looking at the OD circuit just as some of you already have gone thru. I haven't yet changed much though. No MV cap at all. I did add an enhancement cap across the PI entrance plate resistor, didn't notice much if any difference.

I have checked the coupling caps for DC leakage, they are clean.

Below is my build, it's pretty much all NOS caps and resistors. Light blue Electra MF7C plates, Piher/Iskra CF cathodes, Mial 270pF polystyrene snubbers, from grid to cathode, not plate to cathode.

V2A gridstopper is a 1/3W 68K Piher CF. I have been wondering if this is too low a wattage value, and after I saw TM's builds again with 1W Pihers in that spot I am definitely going to try that.

As an aside (sort of), my PS is different than the original. It's a FW not a FWB and runs plates/screens in idle at 441V which is a good 20V low from HAD's spec. Wondering if I should change that PT out.

Have not yet really looked over my lead dress. Need to do that.

Any comments/suggestions would be most welcome.

[aflynt]

Very timely thread for me. I have been trying to figure out how to tweak my #102 to get rid of the OD hash.

Bearing in mind that the amp is not yet broken in, not enough hours on it by far, I am now looking at the OD circuit just as some of you already have gone thru. I haven't yet changed much though. No MV cap at all. I did add an enhancement cap across the PI entrance plate resistor, didn't notice much if any difference.

I have checked the coupling caps for DC leakage, they are clean.

Below is my build, it's pretty much all NOS caps and resistors. Light blue Electra MF7C plates, Piher/Iskra CF cathodes, Mial 270uF polystyrene snubbers, from grid to cathode, not plate to cathode.

V2A gridstopper is a 1/3W 68K Piher CF. I have been wondering if this is too low a wattage value, and after I saw TM's builds again with 1W Pihers in that spot I am definitely going to try that.

As an aside (sort of), my PS is different than the original. It's a FW not a FWB and runs plates/screens in idle at 441V which is a good 20V low from HAD's spec. Wondering if I should change that PT out.

Have not yet really looked over my lead dress. Need to do that.

Any comments/suggestions would be most welcome.

I used a very similar resistor-compliment on my first #102 build. I wound up replacing the 1/3 watt Piher grid stoppers with new 2Watt KOA Speer Carbon films (the light green ones). Tonally, I didn't really hear much of a difference, but the KOA Speers did seem quite a bit less noisy.

As for plate voltage, I definitely liked the amp around 460 - 470 better than 440. It just seemed more consistent and solid sounding and feeling.

Maybe try playing around with lead-dress around V1 and V2 and experiment with capacitance around the loop? That's what ironed things out the most for me.

-Aaron

[David Root]

Thanx Aaron, very helpful, especially on the B+ voltage, I had no reference on that.

[ToneMerc]

Tonally, I didn't really hear much of a difference, but the KOA Speers did seem quite a bit less noisy.

-Aaron

David, that's the only reason I use the 1 watt verses 1/2 watt in the OD entrance and at the grid inputs. If I could make one component change, I would try CF on the plates verses the Electra. I wish I could hear it.

What tube is in V2 and what are your preamp voltages?


TM

[JazzGuitarGimp]

Mial 270uF polystyrene snubbers, from grid to cathode, not plate to cathode.

Hi David,

I think you meant 270pF, not uF. But that is not what caught my attention: Since the grid and cathode signals are in phase with each other, I question the efficacy of placing snubbers here. I would think from plate to grid, or from grid to cathode will accomplish a high-end rolloff, which I think is the goal of the snubbers. Correct me if I am wrong.

Cheers,
Lou

[ToneMerc]

Mial 270uF polystyrene snubbers, from grid to cathode, not plate to cathode.

Hi David,

I think you meant 270pF, not uF. But that is not what caught my attention: Since the grid and cathode signals are in phase with each other, I question the efficacy of placing snubbers here. I would think from plate to grid, or from grid to cathode will accomplish a high-end rolloff, which I think is the goal of the snubbers. Correct me if I am wrong.

Cheers,
Lou

That's a good point because if you were going to put a snubber on the grids, wouldn't a better location would have been across the grid resistors?

David, why did you decide not to do the plate>cathode snubber scheme?

TM