Well, that would explain what HAD did it and why. If that be so, it begs at least two other questions.
One is when Ayan played #124 and documented the session, was it thru a 4 ohm or 8 ohm cabinet? He could have used either, but only he knows!
Hopefully he will remember.......??
The other question is, if all the #124 clones, including my own, using either a std. Twin OT at 4 ohms only or a 4/8/16 modern version, can they ever sound quite the same owing to an "in-between" 4 and 8 ohms OT being used in the original?
#124 Output Transformer
Moderators: pompeiisneaks, Colossal
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David Root
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Re: #124 Output Transformer
The amp was played using a 1x12 EVM 12L cabinet, 8 ohms load.David Root wrote:Well, that would explain what HAD did it and why. If that be so, it begs at least two other questions.
One is when Ayan played #124 and documented the session, was it thru a 4 ohm or 8 ohm cabinet? He could have used either, but only he knows!
Hopefully he will remember.......??
The other question is, if all the #124 clones, including my own, using either a std. Twin OT at 4 ohms only or a 4/8/16 modern version, can they ever sound quite the same owing to an "in-between" 4 and 8 ohms OT being used in the original?
Cheers,
Gil
Re: #124 Output Transformer
1700 or so is the same specs as some Marshall irons.
One of the best sounding civilian owned Dumbles I know uses 1700 marshall iron.
One of the best sounding civilian owned Dumbles I know uses 1700 marshall iron.
"...& I'm all out of bubblegum"
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David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: #124 Output Transformer
Thank you Gil!
Ampdork, that is on the short side too, I have a 17xx Marshall 100W OT, perhaps I should check that out on my #124.
Ampdork, that is on the short side too, I have a 17xx Marshall 100W OT, perhaps I should check that out on my #124.
Re: #124 Output Transformer
Hey, that's very interesting that the cab was 8 Ohms. So, going with the turns ratio of 18.3:1, an 8 Ohm cab would reflect an impedance of 2679 Ohms! So, in this case, the gradient of the load line has actually dropped!!...which would generally push the output stage characteristics a little more into the kinked area of the grid curves...
Also, looking at the photo's of the amp's rear panel, it still says "4 Ohm load" ie. the expectation would be that a 4 Ohm load would still be permissable - if HAD had set the turns ratio just for 8 Ohm cabinets, then you would perhaps have thought that he'd re-label the speaker jacks for an 8 Ohm load only? Either way, if you believe the 18.3:1 turns ratio, the output stage is certainly operating with a non-typical load whatever you plug into it! (ie. 2679 Ohms or 1339 Ohms depending on 8 or 4 ohm cab)
That's one way of helping to get a unique sound I suppose !
Pete
Also, looking at the photo's of the amp's rear panel, it still says "4 Ohm load" ie. the expectation would be that a 4 Ohm load would still be permissable - if HAD had set the turns ratio just for 8 Ohm cabinets, then you would perhaps have thought that he'd re-label the speaker jacks for an 8 Ohm load only? Either way, if you believe the 18.3:1 turns ratio, the output stage is certainly operating with a non-typical load whatever you plug into it! (ie. 2679 Ohms or 1339 Ohms depending on 8 or 4 ohm cab)
That's one way of helping to get a unique sound I suppose !
Pete
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David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: #124 Output Transformer
It moves it as far below the knee with 8 ohms as it was above the knee with 4 ohms. So if it were a 6 ohm cab it would be right on the knee. (Interpolating a 420V G2 plate curve).
Isn't the EV 12 actually nearer 6 ohms than 8....??
Isn't the EV 12 actually nearer 6 ohms than 8....??
Re: #124 Output Transformer
Kimock prefers running his amps into 16 ohm cabinets, and SRV's vibroverbs ran a 2 ohm fender tranny into an 8 ohm EVM 15L speaker. These are guys that like a pretty clean tone.
EV and other speakers can often be around 6 ohms DCR, but DCR doesn't tell the whole story.
Another impedance mismatch going the other direction is the old 3-10" bandmasters with a 4 ohm tranny and a 2.8 ohm speaker load, pretty loose sounding amps (for a lot of reasons) that broke up easier than the similar circuit pro's and supers.
Definitely an area for experimentation, but I think I would get a general idea using various speaker loads before I started adding or removing tranny windings. You really want to look at load lines to see where things are at, realizing impedances will be reflected all the way up the chain. After many years of meditating on the subject, I'm begining to think that impedance matching is a HUGE part of what people define as "synergy". Paying just a little attention to circuit constants and energy transfer can really help. The hi-fi guys have been chasing their tails on this one for years causing people to spend lots of money trying to find that ever elusive "synergy".
Impedance matching covers the whole gamut from guitar construction to speaker effciency and cabinet design, from fingers to ears and everything inbetween. Any "tweaks" really only add too or take away from this factor.
-ER
EV and other speakers can often be around 6 ohms DCR, but DCR doesn't tell the whole story.
Another impedance mismatch going the other direction is the old 3-10" bandmasters with a 4 ohm tranny and a 2.8 ohm speaker load, pretty loose sounding amps (for a lot of reasons) that broke up easier than the similar circuit pro's and supers.
Definitely an area for experimentation, but I think I would get a general idea using various speaker loads before I started adding or removing tranny windings. You really want to look at load lines to see where things are at, realizing impedances will be reflected all the way up the chain. After many years of meditating on the subject, I'm begining to think that impedance matching is a HUGE part of what people define as "synergy". Paying just a little attention to circuit constants and energy transfer can really help. The hi-fi guys have been chasing their tails on this one for years causing people to spend lots of money trying to find that ever elusive "synergy".
Impedance matching covers the whole gamut from guitar construction to speaker effciency and cabinet design, from fingers to ears and everything inbetween. Any "tweaks" really only add too or take away from this factor.
-ER
Re: #124 Output Transformer
Try using a 1KHz signal and measuring V/I and see what you get -- have never tried it myself.David Root wrote:It moves it as far below the knee with 8 ohms as it was above the knee with 4 ohms. So if it were a 6 ohm cab it would be right on the knee. (Interpolating a 420V G2 plate curve).
Isn't the EV 12 actually nearer 6 ohms than 8....??
Gil
nominal impedance
just consider that speakers nominal impedance is usually measured at 1khz and look at impedance curves from datasheets: nowhere near that value elsewhere...
Odd Ball Transformer
Dredging up an old thread. 124 18.3:1 OT winding ratio.
I recently purchased an old transformer on ebay:
Fender 125A16A Date Code 606233 (no dashes) -1962?
Cannot find a single reference to the A16A.
Appears very similar to a Twin Reverb transformer but the winding ratio is 17.4:1.
I'm gathering parts for a 124-ish build and thinking this might be a decent place for this transformer to land.
I recently purchased an old transformer on ebay:
Fender 125A16A Date Code 606233 (no dashes) -1962?
Cannot find a single reference to the A16A.
Appears very similar to a Twin Reverb transformer but the winding ratio is 17.4:1.
I'm gathering parts for a 124-ish build and thinking this might be a decent place for this transformer to land.
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PaisleyTube
- Posts: 208
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- Contact:
Re: #124 Output Transformer
don't mind* the "mismatching"; it's all about sound and touch-respsonse. Most of the time I also prefer mismatching sf OTs.
* but please do!, ha ha
* but please do!, ha ha
Chris
Love, peace & loudness!
Love, peace & loudness!
If you had to choose
I guess my question is:
If you had to choose between a vintage Fender transformer that either resolves to the correct part number (022889) or the correct winding ratio (18.3:1) which one would you choose if your goal was to have the amp sound more like 124?
If you truly believe the little blue sticker the answer is obvious. So then I think I'm asking do folks believe the winding ratio on that transformer is 18.3:1.
If you had to choose between a vintage Fender transformer that either resolves to the correct part number (022889) or the correct winding ratio (18.3:1) which one would you choose if your goal was to have the amp sound more like 124?
If you truly believe the little blue sticker the answer is obvious. So then I think I'm asking do folks believe the winding ratio on that transformer is 18.3:1.
Re: #124 Output Transformer
Hello. Ive been hanging around the forum but i would like to say on the matter of the output transformer. Im building BM the transformer i choose is a fender tonemaster. The primary is 2350ohms secondary is 4/8/16. I choose this because its the closest to jj6l6gc rated 2.5k for four tubes. From the Hamm radio guys and hifi guys i have learned that the closer the impedance are matched from the plate to transformer makes the power transfer high. So for the D style pre amp distortion and clean power section. It makes sence that HAD matched them closey for peak power transfer. Just my two cents.