Stephen1966 wrote: ↑Fri Apr 28, 2023 1:17 pm
Ian, did you notice it more during the attack as well?
I too initially preferred the fuller tone as it seemed to push the lower mids a little more but after playing both over the course of a week I gravitated towards the direction that gives more clarity. I had also done a few resistor changes (swapped late 70s pihers for the earlier version with round end-caps) and this seemed to darken the amp up a little bit. When I changed the choke "polarity" it cleared up the muddiness. Notes are clearer and you can hear more definition in the lower registers.... a crispness in the attack
Cab arrived yesterday and spent a ton of time making a drilling template to mount the chassis (custom mounting holes). Amp is in and there was a surprising difference in tone. I have a similar EVM 12S and when I had the amp going through my 2x12 EVM12S cab, it sounded great on the top-end with tons of bottom end. I expected the combo with single 12S (4Ohm to 8Ohm mismatch) to reduce some of the bass which it has but it has also reduced some of the highs. This actually turned out great as the "accent" switch was pretty useless (too bright). I was wondering why HAD used a 1uf presence cap but if he as tuning the amp for a combo with impedance mismatch, that may explain it.
The amp is sounding well-balanced and has a beautiful singing sustain with HBs and SCs, even on clean. I am still tweaking the OD pot. I currently have a 100K linear that measures 125K. In talking with an owner of a 2nd/3rd Gen amp, the OD pot measured 90K. I have been testing with a 470K strapped over the pot and there is a definite reduction in bass with the pot closer to 100K.... I just can't decide which I prefer
PXL_20230501_025102623.jpg
You do not have the required permissions to view the files attached to this post.
Hi Ian,
I know I’m months behind on this, but fantastic build! Just the metal work is impressive - but the innards are what I’ve come to see as the very meticulous build methods (which I try to copy anywhere I can) common to all your builds, not to mention the NOS bits and pieces. Certainly impressive!
One question for you:
What swayed you to a 3rd gen vs 2nd gen?
Trying to decide which one to try next myself. I like my 102, but looking for something with more “scream” to it. I’ve heard that word used to describe both gens in other threads, but see there are some fundamental differences in the tone stacks - so I’m not sure how that relates practically. Seems like everything you build has a huge amount of forethought and consideration; so I suspect you have some solid reasoning for your choice here, so wanted to ask. Doing my research and just read this whole thread. Really informative!
Raoul Duke wrote: ↑Tue Jan 23, 2024 12:58 am
Hi Ian,
I know I’m months behind on this, but fantastic build! Just the metal work is impressive - but the innards are what I’ve come to see as the very meticulous build methods (which I try to copy anywhere I can) common to all your builds, not to mention the NOS bits and pieces. Certainly impressive!
One question for you:
What swayed you to a 3rd gen vs 2nd gen?
Trying to decide which one to try next myself. I like my 102, but looking for something with more “scream” to it. I’ve heard that word used to describe both gens in other threads, but see there are some fundamental differences in the tone stacks - so I’m not sure how that relates practically. Seems like everything you build has a huge amount of forethought and consideration; so I suspect you have some solid reasoning for your choice here, so wanted to ask. Doing my research and just read this whole thread. Really informative!
Thanks!
Marc
Hey Marc,
Thank you for the kind words.
I did do a bunch of research before building it and from what I could tell, I'd probably be happy with either. My decision really came down to some of the parts that I had were more suited to doing an accurate 3rd Gen. I have since updated it with "more" correct Tandy Coax and a period correct relay - I must say it's one of my favorite amps.
PXL_20240223_170331741.jpg
PXL_20231206_025811009.jpg
If you do end up building this amp (and this may apply to the 2nd Gen) I strongly suggest you build it in a combo or at least run it with the 4Ohm into an 8Ohm speaker. I believe HAD specifically voiced these amps to run this way. When I first finished the amp I ran it into a 2 x 12 EV 12L 4Ohm cab and it was way too bright. The accent switch was unusable and I was starting to regret building it. As soon as I installed it in its cab with an EVM 12S 8Ohm it sounded amazing. Everything balanced out and I could use the accent switch. I preferred the EV 12S over the 12L for this amp.
You do not have the required permissions to view the files attached to this post.
Last edited by ijedouglas on Sat Feb 24, 2024 1:34 am, edited 1 time in total.
Great advice, thank you!
I’ve read about the impedance mismatch, but it always seems a bit speculative. If you’ve tested it and used it for awhile and it’s proven itself - that would seem to be more conclusive. I’ll definitely try it out. Speakers are always a crapshoot for me but my hearing isn’t the greatest - so what sounds good today might sound bad tomorrow, but I digress, lol.
The period-correctness right down to the ice cube relay is pretty astounding. I’ve toyed with the idea of trying that as well. They seem to pop-up on e-bay every so often (more than I’d expect anyway). Looking at yours to include the cabinet is what I’d imagine a new one would have looked like in the ‘70s.
Raoul Duke wrote: ↑Tue Jan 23, 2024 3:37 pm
Great advice, thank you!
I’ve read about the impedance mismatch, but it always seems a bit speculative. If you’ve tested it and used it for awhile and it’s proven itself - that would seem to be more conclusive.
EVH did it with his Marshalls . Dumble did it with his ODS. Plenty of testimony from forum members over the years. Try it for only a moment and there is no speculation … unless you are hearing impaired
Great to know, thanks Charlie! I’m definitely going to try it - even with the amps I have here now.
Just doing more research to determine which types can handle it and which can’t.
Any “rule of thumb” to this regarding type of circuit or which mismatch is safer, i.e. “4-8 is safer than 8-16, AB handles it better than SE, amps with/without NFB are safer”?
Searching that type of thing now, but since it came up - thought I’d ask.
My hearing is or isn’t impaired depending on who you ask, lol. For instance - the USAF said it is during my retirement physical, but the VA says it isn’t “impaired enough”. My wife says it’s selective. She’s probably right…
Ahh, ok thanks Ian!
Funny, I was just on their site looking at small batches of colored wire (didn’t realize they had it).
By the description, it seems like it’ll be easier to cut than the G10.
Raoul Duke wrote: ↑Tue Jan 23, 2024 8:32 pm
Great to know, thanks Charlie! I’m definitely going to try it - even with the amps I have here now.
Just doing more research to determine which types can handle it and which can’t.
Any “rule of thumb” to this regarding type of circuit or which mismatch is safer, i.e. “4-8 is safer than 8-16, AB handles it better than SE, amps with/without NFB are safer”?
Searching that type of thing now, but since it came up - thought I’d ask.
My hearing is or isn’t impaired depending on who you ask, lol. For instance - the USAF said it is during my retirement physical, but the VA says it isn’t “impaired enough”. My wife says it’s selective. She’s probably right…
Thanks again!
As long as it’s halved it’s fine. 4-16 the flyback voltages increase enough to possibly concern , depending how hard you are pushing the amp .fwiw: EVH- 8-16
…the funny thing about men and women with hearing … women speaking in high tones do not inherently trigger our brain neurons into an emotional response …only low toned voices do that I.e. radio voice . So don’t beat yourself up too bad if you seemingly go deaf when the ladies begin crying and screaming about how you don’t hear anything lol…
martin manning wrote: ↑Wed Jan 24, 2024 11:25 pm
An 8 ohm load on a 4 ohm output is going to be harder on the power tube screens, especially if you play at near full power.
Hey Martin, what is your reasoning for this?
"Education is what you're left with after you have forgotten what you have learned" - Enzo
martin manning wrote: ↑Thu Jan 25, 2024 1:34 pm
The load line drops below the Vg1=0 knee, and that causes the screen current to spike when the tube is driven hard.
EVH had a history of pushing his amps very hard with this setup , and the subsequent history of his constant repairs would serve as evidence of such . Popping power tubes with high screen current can make the magic smoke escape . Lowering the voltage with a variac becomes helpful
Fortunately with the ODS most people utilize these at clean headroom volumes, that’s what the built in overdrive is for, hence logically I don’t hear much complaining from users.
