non-HRM Opinions Sought

[dogears]

Yeah..

To my ears, the lower plates break up earlier allowing the extra bass to be more organic. The big plates headroom turns the extra bass into thud and buzz, to me. Also, the lower plates have less bass due to the smaller cathode resistors as well as the lower plate resistance acting against the couplers.... This is all fact that can be demonstrated with the RC formulas.

Never mind. You said high plate resistors.

[ElectronAvalanche]

Hi Jelle,

Have you tried increasing the PI cathode resistor like the Mojave amps and Budda do? The sound gets a bit dark when attenuated heavily with this mod. Larry advised us to use a .0047 or bigger pi cathode bypass cap to cure this. I have not tried this yet..


Is this what you are talking about?

It was not the faux power reduction ala Mojave. The switch messed with one side of the PI. It made a big noise when switching from full to starved and there was a pronounced mid cut. I had only very little time to look at the details, but I think it messed with one of the 1M grid resistors. I need to check my notes and experiment a bit with it. On the other side, Dumble only used this in some very early amps, so it was probably nothing for him to write home about or keep in his amps.

Cheers,

DominiK

[hipbluescat]

Hello

Excuse my ignorance but on the standard D'Lite kit what does it have ?

Is there any modification that I need to do to the standard circuit ?

Regards

[jelle]

Dominik,

Thanks for the info! Please look at the notes and let me know how this worked. I'd be interested to know!

Jelle

[bcook]

When I switched my cathode resistors from CC to RN65, it made a large difference in the smoothness of the response. If I remember correctly, 124 used metal film cathode resistors. I wonder if the harshness in some amps could be attributed to using the "wrong" resistors.

[Pete]

Hello

Excuse my ignorance but on the standard D'Lite kit what does it have ?

Is there any modification that I need to do to the standard circuit ?

Regards

I'm not very familiar with the design but I think it is basically HRM platform & values with no post overdrive trimmers (tone stack), HTH.
As for mods you may need to clarify "standard circuit", I think someone here knows if there is a "final" schem/layout on file.

When I switched my cathode resistors from CC to RN65, it made a large difference in the smoothness of the response. If I remember correctly, 124 used metal film cathode resistors. I wonder if the harshness in some amps could be attributed to using the "wrong" resistors.

RN65 is the standard to use (for any values) as far as my comparisons go and IMHO.

[mlp-mx6]

I'm not very familiar with the design but I think it is basically HRM platform & values with no post overdrive trimmers (tone stack), HTH.

I believe HRM means that it DOES have the post-OD tone stack. Non-HRM has no post-OD stack. There are other differences, but that is the primary one.

The D'Lite is a good-sounding non-HRM amp. Try it as-is before you determine the need for any modifications.

[Pete]

I believe HRM means that it DOES have the post-OD tone stack. Non-HRM has no post-OD stack. There are other differences, but that is the primary one.

The D'Lite is a good-sounding non-HRM amp. Try it as-is before you determine the need for any modifications.

Yes HRM is post OD stack (among other specific circuit characteristics).
I was just trying to say that it has the higher plate/cathode values as in HRM, not 100K/1.5K plate/cathode as discussed earlier in this thread. Sorry for the confusion.

[TimS]

Can you get close to the sound of the lower values by running the preamp volume lower on an amp with the higher values?

[TimS]

Also, when you talk about the lower values having a "harsh" OD sound, do you mean "harsh by Dumble standards, but not necessarily bad sounding depending on what you're after" or "just plain crappy"?

[Normster]

Sorry, late to the party. I just wanted to clear something up regarding the D'Lite cathode bypass values. The D'Lite uses 10uF bypass caps on CL1&2 because that's what sounded best with the OPT we used. Our original intent was to get big sound at a low volume (in a small package). To accomplish that, we took great liberties with the hybrid-a design. In the end, the values we used seemed to give the most pleasing result based on Vibroverb iron and 6V6 output tubes. As Scott keeps reminding us...it's a system.

FWIW, we use more traditional values when using larger iron and 6L6's.

[jaysg]

I stand by my comment that a .05uf coupler on high plate load amps, with 4.7uf bypass, is thuddy and buzzy in the OD (as well as NEVER being documented as being in a Dumble).

Is there a well documented non-HRM amp with high value plate resistors out there? I'm just trying to make sense of it and refine my amp.

CL1 220K, 3K3, 5uF
CL2 150K, 2K2, 5uF...will try 1.0uF someday, .047uF pass cap
OD1 180K, 2K7, 5uF, .022uf pass cap
OD2 120K, 1K8, 1uF, .005uF pass cap
2/4/8 Super Reverb OT fwiw, and thanks to everyone responsible for turning me onto the Vishay MFs and MPPs.

[dogears]

Yep.... It had a .01uf and not a .05uf!!

I'd use a .02uf

Also, the .022uf on OD1 needs to be reduced to .01uf.

Bypass on OD2 is 4.7uf

I stand by my comment that a .05uf coupler on high plate load amps, with 4.7uf bypass, is thuddy and buzzy in the OD (as well as NEVER being documented as being in a Dumble).

Is there a well documented non-HRM amp with high value plate resistors out there? I'm just trying to make sense of it and refine my amp.

CL1 220K, 3K3, 5uF
CL2 150K, 2K2, 5uF...will try 1.0uF someday, .047uF pass cap
OD1 180K, 2K7, 5uF, .022uf pass cap
OD2 120K, 1K8, 1uF, .005uF pass cap
2/4/8 Super Reverb OT fwiw, and thanks to everyone responsible for turning me onto the Vishay MFs and MPPs.

[jurgen]

Sorry, late to the party. I just wanted to clear something up regarding the D'Lite cathode bypass values. The D'Lite uses 10uF bypass caps on CL1&2 because that's what sounded best with the OPT we used. Our original intent was to get big sound at a low volume (in a small package). To accomplish that, we took great liberties with the hybrid-a design. In the end, the values we used seemed to give the most pleasing result based on Vibroverb iron and 6V6 output tubes. As Scott keeps reminding us...it's a system.

FWIW, we use more traditional values when using larger iron and 6L6's.

Hi Norm
I was wondering about this very thing. So does the d'lite44 kit ship with something other than 10u ?

[ayan]

I stand by my comment that a .05uf coupler on high plate load amps, with 4.7uf bypass, is thuddy and buzzy in the OD (as well as NEVER being documented as being in a Dumble).

Is there a well documented non-HRM amp with high value plate resistors out there? I'm just trying to make sense of it and refine my amp.

CL1 220K, 3K3, 5uF
CL2 150K, 2K2, 5uF...will try 1.0uF someday, .047uF pass cap
OD1 180K, 2K7, 5uF, .022uf pass cap
OD2 120K, 1K8, 1uF, .005uF pass cap
2/4/8 Super Reverb OT fwiw, and thanks to everyone responsible for turning me onto the Vishay MFs and MPPs.

I have seen more than one high plate amp, non HRM, but they have been 220K/150K for both V1 and V2, have had a 1uF bypass cap on V2 and a .047 CL2 coupling cap. An earlier version was the same, but with a .022 CL2 coupling cap.

Cheers,

Gil