I don't remember all the exact values that I have seen in pictures or in person, but as far as I can remember, completely identical values of both resistors are more the exception than the rule.
But as far as I know some members here offer commercial replicas of 100W and 150W SSS. So they will probably know the exact values of the original amps (?). So you could maybe ask these members, too?
And even if someone knows the procedure recommended by A. Dumble, he could of course choose a different procedure if he personally likes the tonal and musical results of a different procedure better. Personal taste is often very different.
BTW: Could you perhaps post or link a picture of SSS #014 here, or is the 1 a typo and you mean SSS #004?
Last edited by Max on Wed Nov 10, 2021 9:15 am, edited 1 time in total.
Max wrote: ↑Wed Nov 10, 2021 8:58 am
I don't remember all the exact values that I have seen in pictures or in person, but as far as I can remember, completely identical values are more the exception than the rule.
But as far as I know some members here offer commercial replicas of 100W and 150W SSS. So they will probably know the exact values of the original amps (?). So you could maybe ask these members, too?
And even if someone knows the procedure recommended by A. Dumble, he can of course choose a different procedure if he personally likes the tonal and musical results of a different procedure better. Personal taste is often very different.
BTW: Could you perhaps post or link a picture of SSS # 014 here, or is the 1 a typo and you mean SSS # 004?
Hi Max, its DL #014 which you know fairly well, which uses the SSS power section, and its part list has been deeply discussed here. Also from my knowledge the matched plates are not the exception, but obvioulsy happy to be corrected if others have better first had info
As a matter of fact I am personally unaware of any SSS which does not have same values in both plates, but happy to have your input if you have further knowledge on this
For example SSS #003 doesn't have the same values.
Incidentally, if I were you, A. Dumble's advice would not really matter if I personally liked the results of my own approach better than the results of the procedure suggested by Ampeg for the SVT.
Max wrote: ↑Wed Nov 10, 2021 10:26 am
For example SSS #003 doesn't have the same values.
Incidentally, if I were you, A. Dumble's advice would not really matter if I personally liked the results of my own approach better than the results of the procedure suggested by Ampeg for the SVT.
Which values does it have, if you dont mind me asking?
I don't remember the exact values. But AFAIR they are somewhere between 100k and 150k and their difference is 10k. I also can't remember the exact value of the "Dynamic Balance" control, but based on some other amplifiers, a value of 10k, for example, would seem plausible to me.
BTW: AFAIK SSS100W #003 is back in the US since many years after its stay in Japan. So maybe other members here know the exact values.
I would like to add, that having the right set of power tubes makes a difference as well. I had been using Tung Sol 6L6s which I think are very hot. I changed these for grade 5, Groove Tubes (aka JJ) 6L6s and the amp came alive. Bigger differential between control grid and plate voltages and the amp just blooms. My take on the previous posts - the singular most important piece of advice - is to set the volume and gain to "normal" playing levels. I monitored the FFT with the probe on the 4ohm (GFB) junction. Second harmonic can be seen there, and adjusted to suit your preference. A 1kHz sine wave, is a good starting point. Let your ears be the guide.
Frequency Analyzer plugin on PC; For Ox Box users, or other speaker sims that have a option to bypass the speaker impulse response:
Audio generator sine wave in PI-->>Speaker out amp to Ox Box(bypassed impulse response)
---> Ox Box digital out to Sound card digital in---> Digital in used for a track in a DAW(Pro tools/Cubase)----> insert the free plugin Blu Cat FreqAnalyst---->
While turning the PI trim pot look for minimising the 2nd harmonic(I use 100Hz so 2nd harmonic is 200Hz).
In my case differences, with 3 different amp, were 15-20dB compared to a unbalanced PI trim.
Many thanks Erwin. I looked at the Ox Box but I'm afraid it's well out of my price range. If I might suggest though, there is (possibly) another way to finding the balance which is really non-scientific but which does seem to yield positive results.
I have been using a 1 kHz sine at the input and with the volume and master to something like ordinary playing levels, I simply listened for the oscillation in the OT! I find that the extremes of the trimmer induce an audible oscillation of the OT whereas (in mine) in the 12 o'clock position the OT goes quiet. It's very rough at that point but after playing with it a bit, you get the picture that the balance is somewhere between 11 and 1 o'clock. It's handy to have a few samples on a looper because then you replace the dummy load with the speaker and just try fractionally moving the trimmer until you hear something like the sweet spot. At this point, I've been disabused of the notion that note bloom comes from the PI - at least not entirely - and the "sweet spot" is just a suggestion of a deeper harmonic structure to the notes. Mine, is currently around the 4 minutes to midnight position and at the right gain levels, the notes just take off. And great sustain especially in the higher mid range.
I would welcome any feedback on this idea because this is entirely hypothetical on my part but after spending many hours with a scope and FFT I can say, that this down and dirty method yields results that I can "more measurably" hear. It's subtle, to be sure, but once you tune your ear into it, the note structure is distinct and audible. Seriously, I'm surprised no-one else seems to have mentioned this before. I might be way off but if the sound makes me happy (which it does) there is possibly something more to this. I wouldn't ditch the scope - it's helped me track down quite a number of issues - but in this case, all I really needed was my ears.
Stephen1966 wrote: ↑Tue Apr 19, 2022 7:22 pm
Many thanks Erwin. I looked at the Ox Box but I'm afraid it's well out of my price range. If I might suggest though, there is (possibly) another way to finding the balance which is really non-scientific but which does seem to yield positive results.
I have been using a 1 kHz sine at the input and with the volume and master to something like ordinary playing levels, I simply listened for the oscillation in the OT! I find that the extremes of the trimmer induce an audible oscillation of the OT whereas (in mine) in the 12 o'clock position the OT goes quiet. It's very rough at that point but after playing with it a bit, you get the picture that the balance is somewhere between 11 and 1 o'clock. It's handy to have a few samples on a looper because then you replace the dummy load with the speaker and just try fractionally moving the trimmer until you hear something like the sweet spot. At this point, I've been disabused of the notion that note bloom comes from the PI - at least not entirely - and the "sweet spot" is just a suggestion of a deeper harmonic structure to the notes. Mine, is currently around the 4 minutes to midnight position and at the right gain levels, the notes just take off. And great sustain especially in the higher mid range.
I would welcome any feedback on this idea because this is entirely hypothetical on my part but after spending many hours with a scope and FFT I can say, that this down and dirty method yields results that I can "more measurably" hear. It's subtle, to be sure, but once you tune your ear into it, the note structure is distinct and audible. Seriously, I'm surprised no-one else seems to have mentioned this before. I might be way off but if the sound makes me happy (which it does) there is possibly something more to this. I wouldn't ditch the scope - it's helped me track down quite a number of issues - but in this case, all I really needed was my ears.
Stephen
Hi Stephen. I was curious to see what your voltage difference was between the pins of the trimmer when you found the sweet spot. Was it anywhere close to 6V?
