New ODS 100W build with pictures...

[dogears]

Fwiw, changing a 470pf to a 500pf, can definately have a subtle but noticeable effect. It depends on the use of the cap. In the case of a grid bypass, given the tolerences, you may have more than a 10% change in value and the knee frequency of the high pass will be lowered a bit more into the meat. Run the RC network formulas. For example, if the knee changes from 1900hz to 1750 hz, would that not be a subtle boost to the upper mids??

I don't quite see the point in changing component values as you have listed. It will not provide you with any different tone, going from 470p to 500p. Capacitor types can have an impact on sound, but off course not as much as component value itself.

[Fischerman]

I know that swapping a 470pF for a 500pF at the entrance of the Return stage in the D-Lator in my amp made a slight but noticeable difference. For lack of a better word...the 470pF had slight 'boxiness' to the tone compared to the 500pF (IOW, the mids were affected). But that's just one amp and one person's perception of what they heard.

[bluesfendermanblues]

fair enough guys I rest my case

[ic-racer]

I don't quite see the point in changing component values as you have listed. It will not provide you with any different tone, going from 470p to 500p. Capacitor types can have an impact on sound, but off course not as much as component value itself.

Only one way to find out...

What's the point in having an amp identical to #124, you never played the amp, heard a soundbite of it.

Exactly the point! I want to know what a real Dumble ( #124 in particular) sounds like with my playing, so I'm building an exact replica to find out!

It sounds to me like you should build yourself an additional amp.

Done... ( https://tubeamparchive.com/viewtopic.php?t=5396 )

I understand exchanging sound files and mod ideas, but not the strive to have an amp with visually identical interior. Just my tow (european) cents.

The word 'clone' gets thrown around a lot. It should mean "identical," but no one in the amp hobby uses the term that way. Perhaps I should call my amp a 'Historic Recreation' or something like that. Therefore, ALL the details are important.

[bluesfendermanblues]

Don't get me wrong, I respect your crave for the ultimate tone. I have the urge...... but still, how do you know that #124 posses the true dumble magic.

I've read a lot about the secret HAD sauce in his amps. But what are the main ingredients ??

a) Voltage values on the the volgtage string
b) Capacitor types....OD 715?
c) resistor types...Vishay-Dale RN65 metal films?
d) Lead dress - plate/cath close to chas, signal ½" above, heaters highest.
e) Cable type and quality - cottenwrap og teflon

How would you rate these ingredients for their importance in the HAD maigc sauce?????

[ic-racer]

Don't get me wrong, I respect your crave for the ultimate tone. I have the urge...... but still, how do you know that #124 posses the true dumble magic.

I've read a lot about the secret HAD sauce in his amps. But what are the main ingredients ??

a) Voltage values on the the volgtage string
b) Capacitor types....OD 715?
c) resistor types...Vishay-Dale RN65 metal films?
d) Lead dress - plate/cath close to chas, signal ½" above, heaters highest.
e) Cable type and quality - cottenwrap og teflon

How would you rate these ingredients for their importance in the HAD maigc sauce?????

Well, this is all speculation on my part, but I have developed a feeling for the way HAD created these amps, but I don't know if it is true. I have degrees in both the arts and sciences, and I am always fascinated by people that can find harmony between the two disciplines.

People with a technical or scientific background want to distill the 'active' components of the amp to find the 'cause' of the good sound. And they want to 'throw out' the insignificant details (wire color, etc.).

My theory is that in HAD's mind, he did not waste time and energy distilling the true causal elements from the 'voodoo' elements. There was never any need to. As long as the amp sounded good, that was all that mattered. He approached it like an artist, yet he also had the technical knowledge to attain his goals. So, I don't know the 'essential' elements, and, perhaps HAD did not either! Since I could consider myself a 'student' of 'amp design,' my duplication of #124 could be analogous to an art student copying a Renoir, or a guitar student playing the Villa Lobos Etudes using the exact Segovia fingerings, etc.

Having said all that, I will render an opinion on the tonal elements:
Voltage values: On my Fender I had a 47k resistor siphoning voltage to ground that I had on a switch. It changed V1& V2 from 180 to 210v. I could not tell the difference when toggling the switch while playing. This is allowing for the 5 seconds it took for the voltage to drop.

Capacitor types/Resistor types: I have not rigged up any apparatus to compare side-by-side so -- 'no opinion' (well, I DO have an opinion, but please, don't hold me to it! I think that two 500p capacitors of different types, ie mica or ceramic, will sound different because neither is exactly 500p, rather than because of composition. But, again, please don't hold me to it.)

Lead Dress: Very influential. My schematics on V2 were identical between my Fender and my #124, but the component location and lead dress were very different in the Fender. The Fender was plagued with oscillations!

Personal opinion: Speakers, Tubes, Output Transformer, component values all made big changes in the sound that were easy to hear. The other stuff is harder for me to hear

[ic-racer]

... but still, how do you know that #124 posses the true dumble magic.

Seriously, Gill played it and said it sounded good. But, even if he had not indicated it was good, the variables with tubes, bias, OD trim and speakers and guitars would still make me think good sounds may still be in there if the right combination of things were attached to the amp.

[ic-racer]

I changed the 'Mid Boost' cap from 330p to 300p.
I changed the 220k bypass cap on V1 from 470p to 500p.
I changed the heater grounds from 220r 5% to 120r 1% (119.6 & 119.7)
I changed the V1 and V2 grid resistors from RadioShack 1/2W to KOA 1W.
I changed the V1 and V2 cathode resistors from RadioShack 1/2W to Vishay/Dale RN65.
I changed the 220k OD entry resistor from RadioShack 1/2W to KOA 1W.
I changed the effects jacks cap from 270p to 250p.
I changed the PI 110k and 120k resistors from 1/2W RadioShack to KOA 1W.

To see if I could hear a difference I changed two 6L6 tube sockets from CC 3.3k/1k5W to CF 5.1K/470R5W. I swapped two tubes back and forth between the two paired sockets and could not hear any difference. I then went ahead an converted them all to 5.1k/470R5W.

So, at this point I have matched layout, component value, component type, component wattage and overall schematic as close as I can.

[joebob]

On the main board what is the wattage rating of the resistors? They appear to be 1w instead of 1/2w. Also what are the dimensions of the main board?

Dave

[ic-racer]

On the main board what is the wattage rating of the resistors? They appear to be 1w instead of 1/2w. Also what are the dimensions of the main board?

Dave

Yes, from what I can tell (and comments from others) the #124 main board resistors, and preamp grid resistors are mostly 1W carbon film. Exceptions are V1,V2 plates/cathodes, slope and NFB resistors.

The plates are V/D RN65
The cathodes are possibly Mepco MF, but the 4 don't look identical.
The slope looks like a Xicon or similar, blue MF.
The NFB looks kind of like a red 3W Vishay BC series, but not exactly.

I can measure my board size and let you know.

[dogears]

You may not hear much of a difference swapping screen resistors from 470 ohm to 1.5K, but you should feel a big difference in the bass. I can feel a big difference between 470ohm and 1K! The bigger the screen resistor, the mushier the bass.

To see if I could hear a difference I changed two 6L6 tube sockets from CC 3.3k/1k5W to CF 5.1K/470R5W. I swapped two tubes back and forth between the two paired sockets and could not hear any difference. I then went ahead an converted them all to 5.1k/470R5W.

So, at this point I have matched layout, component value, component type, component wattage and overall schematic as close as I can.

[ic-racer]

Someone had asked about the size of the preamp board, but I can't find the original post. Anyway, if you are reading this, my preamp board measured 189mm by 69mm.

[ic-racer]

Ok, the last thing to change was the 270p bright cap for a 300p. Again, 'no looking back' with this one. It made the 'BRIGHT' more useable.

So, really, every step toward #124 made it sound better.

I posted a thread a while back that I was disappointed in moving toward the #124 values, but after the complete conversion, I think I have found some real magic in this amp. So much so, I am forcing myself to NOT CHANGE A THING from here on out (note the goo ). At this point I honestly think #124 could have sounded similar when it was new.

Here it is, all finished and ready to go back in the cabinet. After two weeks of on-and-off listening to this amp and the others in the collection, this amp clearly is the standard by which the others are measured.

• clone
  v.
  To produce a copy of; imitate closely

[ayan]

Ok, the last thing to change was the 270p bright cap for a 300p. Again, 'no looking back' with this one. It made the 'BRIGHT' more useable.

So, really, every step toward #124 made it sound better.

I posted a thread a while back that I was disappointed in moving toward the #124 values, but after the complete conversion, I think I have found some real magic in this amp. So much so, I am forcing myself to NOT CHANGE A THING from here on out (note the goo ). At this point I honestly think #124 could have sounded similar when it was new.

Here it is, all finished and ready to go back in the cabinet. After two weeks of on-and-off listening to this amp and the others in the collection, this amp clearly is the standard by which the others are measured.

• clone
  v.
  To produce a copy of; imitate closely

Oh my goodness, the goop looks great! I have to ask, what did you use for the blue and black goo sticky stuff? Love the looks!

Gil

[skyboltone]

You may not hear much of a difference swapping screen resistors from 470 ohm to 1.5K, but you should feel a big difference in the bass. I can feel a big difference between 470ohm and 1K! The bigger the screen resistor, the mushier the bass.

Bummer, I was just about to experiment with that. My screens run filament red hot most of the time. 470ohm. Plates stay grey. Pretty straight forward Rev A with 478VDC on the plates. The showman choke doesn't drop anything at idle. It's got extraordinary bass, I don't wanna screw that up. Maybe it's just the sovteks, I don't wanna risk my Jan/Phillips 5881s yet.

I'm about to rip and run on a #124 setup for it though.

Hey IC, can you hear the goop? Sorry, I haven't been following the thread.