The TT utilizes a five section fully filmed interleaved output transformer that is very closely balanced to primary. The EL84 output tubes are cathode biased to around 90% in the 15w position, and 96% in the 7w position. In short, the Tiny Terror is designed to produce as much gain as a four stage gain pot, but the output tubes are driven evenly all the way through. The tone control is also designed in a unique way, where the tone circuit is not on the preamp side, but actually part of the phase inverter (power amp) so the gain structure of the amp is unaffected by the tone control.
The fundamentals resembles the Vox (or Matchless, often misunderstood by called Class-A amps, but just plain cathode-bias'ed AB's running hot).
The TT tranni is not run-of-the-mill, but any 17 watt single-set El84 should do the basics.
The fundamentals resembles the Vox (or Matchless, often misunderstood by called Class-A amps, but just plain cathode-bias'ed AB's running hot).
The TT tranni is not run-of-the-mill, but any 17 watt single-set El84 should do the basics.
Well, thanks for all that!
I'm thinking more like 8K CT for the primary after looking up the tubes again.
I'd like 4 -8 ohm taps and it looks like the Marshall 18W is best but they
tend to be pricey.
Edcor would probably be excellent but I'd have to ask if a tapped secondary
is an option.
Peter: Do you know the grade of steel used in the TT OEM transformer?
I'm thinking more like 8K CT for the primary after looking up the tubes again.
I'd like 4 -8 ohm taps and it looks like the Marshall 18W is best but they
tend to be pricey.
Edcor would probably be excellent but I'd have to ask if a tapped secondary
is an option.
Peter: Do you know the grade of steel used in the TT OEM transformer?
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Possibly the worst Chinese junk you could think of. In guitar-output transformators it's rather the winding that counts than the quality of the iron. Many old Marshall's got their grunt from core-saturation. The most important thing is if the primary is dimensioned for at given current.
The older amps did use better iron, and not "Chinese junk".
Sunn amps used the excellent Dynaco transformers.
Several companies advertise the use of M-6 core material:
EDCOR Electronics Corporation. Steel Lamination
The non-linear characteristics certainly make a difference when you
are driving the output into hard clipping.
Sunn amps used the excellent Dynaco transformers.
Several companies advertise the use of M-6 core material:
EDCOR Electronics Corporation. Steel Lamination
The non-linear characteristics certainly make a difference when you
are driving the output into hard clipping.
Here is a low cost transformer for a Fender reissueIt is 8K to 8 ohm only but is much smaller than the Marshall 18W and probably not as good - I don't plan to use it:
Fender Output Transformer, Pro Junior
Here is a Marshall drop in replacement, it is larger and has 4,8, and 16 taps. Interesting
that it is designed for 3,7 and 15 ohms and provides an even higher 10K load for normal
loads. 8K was already high, I'd prefer something better matched:
Edit: 10K is what they claimed in the spec but I get 9K which is not too far off:
Marshall Style 18W Output Transformer 4/8/16 Ohm
This is a 15W but rated to 40 Hz so it should do 18 to 22W no problem. They don't have multitap transformers for transformers less than 25W so this 6 ohm might be a good compromise:
EDCOR Electronics Corporation. GXPP15-6-8K
Hammond 1760E or F might be good but I don't think they are the best value:
http://angela.com/hammondoutputtransformer1760e.aspx
I think this is best, 8K CT in 4 and 8 out, decent size and price:
Fender Push-Pull Princeton Reverb Style 15W Output Transformer 4/8 Ohm
Fender Output Transformer, Pro Junior
Here is a Marshall drop in replacement, it is larger and has 4,8, and 16 taps. Interesting
that it is designed for 3,7 and 15 ohms and provides an even higher 10K load for normal
loads. 8K was already high, I'd prefer something better matched:
Edit: 10K is what they claimed in the spec but I get 9K which is not too far off:
Marshall Style 18W Output Transformer 4/8/16 Ohm
This is a 15W but rated to 40 Hz so it should do 18 to 22W no problem. They don't have multitap transformers for transformers less than 25W so this 6 ohm might be a good compromise:
EDCOR Electronics Corporation. GXPP15-6-8K
Hammond 1760E or F might be good but I don't think they are the best value:
http://angela.com/hammondoutputtransformer1760e.aspx
I think this is best, 8K CT in 4 and 8 out, decent size and price:
Fender Push-Pull Princeton Reverb Style 15W Output Transformer 4/8 Ohm
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Hi Guys
Check out the Hammond 1700-series replacement PTs/OTs for guitar amps. Hammond's site has full specs for every part. You can buy them from CE Distribution in the US, and from Hammond dealers around the world.
Great value for the money.
If you wanted to go crazy hi-fi OT-wise, check out the Hammond 1560E which they rate to 70Hz but it actually goes to 7Hz - yes 7Hz!. This was originally a Thordarson design. The 1650E is 15Wrms full audio bandwidth, 8k-aa with UL taps, 4,8,16 taps. I can't vouch for there being enough space on the Vox chassis for this OT.
Our site has full (expanded) specs for the Hammond 1650-series OTs, 200/300-series PTs, and shows how to match PTs to OTs.
Mercury Magnetics OTs are over-hyped junk. I've heard more reports than I can remember from techs installing MM parts due to customer requests only to further replace the MM part with a better-sounding generic replacement.
Have fun
Kevin O'Connor
londonpower.com
Check out the Hammond 1700-series replacement PTs/OTs for guitar amps. Hammond's site has full specs for every part. You can buy them from CE Distribution in the US, and from Hammond dealers around the world.
Great value for the money.
If you wanted to go crazy hi-fi OT-wise, check out the Hammond 1560E which they rate to 70Hz but it actually goes to 7Hz - yes 7Hz!. This was originally a Thordarson design. The 1650E is 15Wrms full audio bandwidth, 8k-aa with UL taps, 4,8,16 taps. I can't vouch for there being enough space on the Vox chassis for this OT.
Our site has full (expanded) specs for the Hammond 1650-series OTs, 200/300-series PTs, and shows how to match PTs to OTs.
Mercury Magnetics OTs are over-hyped junk. I've heard more reports than I can remember from techs installing MM parts due to customer requests only to further replace the MM part with a better-sounding generic replacement.
Have fun
Kevin O'Connor
londonpower.com
Disclaimer: I'm just a hack, certainly not an expert. The guy above is.
Edcor doesn't make a GXPP-line tranny under 25 watts with multiple output taps, but they do in the CXPP line.
So you burned out the original, and want something that won't blow again, but want to keep the tranny's input impedance low and drive it hard, high A/B bias, and need screen taps? More money, but perhaps you could look at transformers rated more than the amp's output power, like the 21-watt Edcor CXPP21-MS-8.6K into 4,8,16 speaker for $56.52 or the 25-watt CXPP25-MS-8K into 4,8,16 speaker for the same $56.52. Wouldn't a higher impedance make less power but be more reliable? There's a huge variation in the power from EL84's, like the Peavey Classic 30 and classic 50 both use 4 EL84's, but one has a lot more output than the other. Good luck.
Edcor doesn't make a GXPP-line tranny under 25 watts with multiple output taps, but they do in the CXPP line.
So you burned out the original, and want something that won't blow again, but want to keep the tranny's input impedance low and drive it hard, high A/B bias, and need screen taps? More money, but perhaps you could look at transformers rated more than the amp's output power, like the 21-watt Edcor CXPP21-MS-8.6K into 4,8,16 speaker for $56.52 or the 25-watt CXPP25-MS-8K into 4,8,16 speaker for the same $56.52. Wouldn't a higher impedance make less power but be more reliable? There's a huge variation in the power from EL84's, like the Peavey Classic 30 and classic 50 both use 4 EL84's, but one has a lot more output than the other. Good luck.
I'm wondering what the physical dimensions are for this transformer if you happen to have them, and also the core dimensions?
Here is a 25W transformer for $34, good deal, but it has a 6.6K primary impedance:
https://www.tubesandmore.com/products/P-TF41318
Probably better suited to 6V6 or 5881s than EL84s.
Even better deal, 25W Deluxe style transformer for $26, 6.6K pri and 8 ohm only sec:
https://taweber.powweb.com/store/041318sch.jpg
It is the W041318 here:
https://taweber.powweb.com/store/magnetic.htm
https://www.tubesandmore.com/products/P-TF41318
Probably better suited to 6V6 or 5881s than EL84s.
Even better deal, 25W Deluxe style transformer for $26, 6.6K pri and 8 ohm only sec:
https://taweber.powweb.com/store/041318sch.jpg
It is the W041318 here:
https://taweber.powweb.com/store/magnetic.htm
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The Weber in the previous post is listed as a Fender 125A1A which is a Deluxe OPT.
Here is another source for it but a bit more expensive at about $30, I don't know if it is from the same company, here it is listed as 20W:
ClassicTone # 40-18002 Fender Deluxe Style 20W Output Transformer 8 Ohm
Here is a version of the Deluxe OPT with a 4/8 ohm output, $37:
Fender Deluxe Style 20W Output Transformer 4/8 Ohm ClassicTone # 40-18038
Here is another source for it but a bit more expensive at about $30, I don't know if it is from the same company, here it is listed as 20W:
ClassicTone # 40-18002 Fender Deluxe Style 20W Output Transformer 8 Ohm
Here is a version of the Deluxe OPT with a 4/8 ohm output, $37:
Fender Deluxe Style 20W Output Transformer 4/8 Ohm ClassicTone # 40-18038
Going to keep output transformer info and links here.
People seem to like Classic Tone output transformers, some say they manufactured them for Fender for many years:
Thoughts on ClassicTone Transformers? - Page 2 - The Gear Page
People seem to like Classic Tone output transformers, some say they manufactured them for Fender for many years:
Thoughts on ClassicTone Transformers? - Page 2 - The Gear Page
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