hello,
I'm looking at building an amp along the lines of the ampeg/guild rt98, I still have to source an ot for it. i'm looking at using one designed for fender deluxe. it would be good if someone take a look at the schematics and let me know if its the best rating and impedance to use for this project? i cant seem to find any info or specs on the originals that were used,
thanks
I'm looking at building an amp along the lines of the ampeg/guild rt98, I still have to source an ot for it. i'm looking at using one designed for fender deluxe. it would be good if someone take a look at the schematics and let me know if its the best rating and impedance to use for this project? i cant seem to find any info or specs on the originals that were used,
thanks
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Fender didn't publish the specs on the schematics because they were not needed. If you needed a new OT for your 5E3, you called Fender or a Fender dealer and ordered a new 5E3 OT.
We can all find our favored impedance ratio transformers, but keep in mind these are just guitar amps, not lab equipment. The tube curves are broad. A zillion 5E3 Fenders used that transformer with one pair of 6V6 for decades. It will work with most any pair of 6V6.
My files do not include any old Ampegs with 6V6, most of them used 7591s. For what it is worth, the OTs on the 7591 amps were also 6.6k. 8k may be closer to a book spec for 6V6, but I have no idea what sonic change it would make if any were audible. Book specs are fine, but remember, Leo fender ran and runs 6V6s are a good 100v over their book spec, and here 60 years later, they are still running.
We can all find our favored impedance ratio transformers, but keep in mind these are just guitar amps, not lab equipment. The tube curves are broad. A zillion 5E3 Fenders used that transformer with one pair of 6V6 for decades. It will work with most any pair of 6V6.
My files do not include any old Ampegs with 6V6, most of them used 7591s. For what it is worth, the OTs on the 7591 amps were also 6.6k. 8k may be closer to a book spec for 6V6, but I have no idea what sonic change it would make if any were audible. Book specs are fine, but remember, Leo fender ran and runs 6V6s are a good 100v over their book spec, and here 60 years later, they are still running.
thanks, I found this product info from one ot retail website, so i think the 6v6 used 6.6k like the 7591
::Ouput transformer OT151A used on most vintage Ampeg combos using cathode biased 6V6 and 7868 and 7591A powr tubes. Has double set of output leads just like the original.
Use for: Jets, Reverberockets, Echto Twins, AC12, Gemini 1 and more.
Made in the USA to original specs by our friends at Heyboer. CE component certified.---
My experience:
I've built 3 off 6V6 push pull Guitar Amps using these output trannies with a B+ of 350V.
86PP output transformer
They are 10K Raa with 20% Ultralinear taps. 20% Ultralinear taps suit 6V6 better than the more usual 43% taps.
8K is the Book value recommendation for 6V6 with +315V HV supply. As you increase the voltage you should actually increase Raa of the output tranny.
In these amps I have the Ultralinear mode switchable. More "mature" (read "old farts") like me seem to prefer Ultralinear Mode, young "shreaders" seem to like it in Pentode mode.
But VERY happy with those output trannies for Guitar.
I also tried these trannies in a HiFi Amp and they were a bit lacking in bottom end for that. I replaced them with Hammond 1609 (at 4 times the price) in the HiFI Amp.
You will find that medium quality HiFi Output Trannies make excellent Guitar Amp trannies.
The Raa is not super critical which is why you see some designs using Raa of 6K6 with quite high B+ voltages. That is just done to screw the very last watt out of the output tubes but you can expect somewhat reduced output tube lifetime.
ASIDE: An 8K Raa output tranny will reflect a 8K load when an 8 Ohm Resistor is connected to the 8 Ohm secondary (or 4 Ohm to the 4Ohm secondary etc.). An 8 Ohm speaker has an impedance which will vary with frequency between say 5 Ohms and 30 Ohms. That speaker then relects a load varying with frequency of 5K to 30K.
So specifying 6K6 , 8K or 10K Raa is all "in the ball park" and quite OK.
Cheers,
Ian
I've built 3 off 6V6 push pull Guitar Amps using these output trannies with a B+ of 350V.
86PP output transformer
They are 10K Raa with 20% Ultralinear taps. 20% Ultralinear taps suit 6V6 better than the more usual 43% taps.
8K is the Book value recommendation for 6V6 with +315V HV supply. As you increase the voltage you should actually increase Raa of the output tranny.
In these amps I have the Ultralinear mode switchable. More "mature" (read "old farts") like me seem to prefer Ultralinear Mode, young "shreaders" seem to like it in Pentode mode.
But VERY happy with those output trannies for Guitar.
I also tried these trannies in a HiFi Amp and they were a bit lacking in bottom end for that. I replaced them with Hammond 1609 (at 4 times the price) in the HiFI Amp.
You will find that medium quality HiFi Output Trannies make excellent Guitar Amp trannies.
The Raa is not super critical which is why you see some designs using Raa of 6K6 with quite high B+ voltages. That is just done to screw the very last watt out of the output tubes but you can expect somewhat reduced output tube lifetime.
ASIDE: An 8K Raa output tranny will reflect a 8K load when an 8 Ohm Resistor is connected to the 8 Ohm secondary (or 4 Ohm to the 4Ohm secondary etc.). An 8 Ohm speaker has an impedance which will vary with frequency between say 5 Ohms and 30 Ohms. That speaker then relects a load varying with frequency of 5K to 30K.
So specifying 6K6 , 8K or 10K Raa is all "in the ball park" and quite OK.
Cheers,
Ian
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