Help With Two Rock OT Swap

[martin manning]

Seems odd. I guess the Classic tone OT is not a Fender Twin type?

[caps8419]

which Classic Tone does the amp currently use?

[Thewayfarer]

Yeah...it looks like a custom order from Marvel. It’s huge too. At least 25% larger than the twin!

[67plexi]

I would leave it stock. I don't see any advantage in swapping transformers.

[Thewayfarer]

You think? I had heard these old seasoned Fender OTs are the best for these style circuits? I found a reputable local tech (Yontz @ Mad Science Raleigh) that can do the mod for me next month.

I'm also trying to inch the Crystal over to as much of JM sig specs as possible - which from what I understand, was Twin Reverb spec transformers. The Crystals beefier OT is one culprit in having too much low end. I've been told that the JM's bass on like 12:00-1:00 is the Crystal on 9:00. I'd like to bring it more in line with a JM Sig

[norburybrook]

You think? I had heard these old seasoned Fender OTs are the best for these style circuits? I found a reputable local tech (Yontz @ Mad Science Raleigh) that can do the mod for me next month.

I'm also trying to inch the Crystal over to as much of JM sig specs as possible - which from what I understand, was Twin Reverb spec transformers. The Crystals beefier OT is one culprit in having too much low end. I've been told that the JM's bass on like 12:00-1:00 is the Crystal on 9:00. I'd like to bring it more in line with a JM Sig

I doubt that's the actual OT. A Beefier OT would probably give you a tighter/cleaner/thicker bottom end, i'e it will produce a firm transient response on the bass strings. The amount of Bass is a different issue.


M

[Thewayfarer]

Got it. Well, it wouldn't hurt to save the money on labor and resell the OT. I have a month before the tech can get it on the bench, so I have a little time to decide.

[Bombacaototal]

On the OT ropic, just a quick question:

It is my understanding that the ideal primary for 25W is 8K, 50W is 4K to 4K2 and 100W is 2K.

For those using the 100W/50W switch do you mismatch the speaker and OT impedance when the amp is set at 50W?

For example using the 4ohm load into 8ohm speaker to turn the 100W OT 2K primary into a 4K primary when the amp is running at 50W?

[norburybrook]

On the OT ropic, just a quick question:

It is my understanding that the ideal primary for 25W is 8K, 50W is 4K to 4K2 and 100W is 2K.

For those using the 100W/50W switch do you mismatch the speaker and OT impedance when the amp is set at 50W?

For example using the 4ohm load into 8ohm speaker to turn the 100W OT 2K primary into a 4K primary when the amp is running at 50W?

Yes, this is the common/Correct way to do it. However I've found OT's to be very accommodating to mismatching so I don't think it's big deal if you don't and prefer the sound.

Marcus

[Bombacaototal]

Thanks Marcus! I appreciate the feedback

Having the option between 60s/70s Fender OT: Vintage (used) or NOS (new old stock - unused), which would you go for?

[norburybrook]

how old is the NOS?

I've had great results with both. My Wonderland used 80's peavey iron and is lovely. Both my #102's I've built sound great. First one had Hammond transformers the second one custom made InMadOut.

I'm still not 100% sure what makes an amp great


M

[Bombacaototal]

how old is the NOS?

I've had great results with both. My Wonderland used 80's peavey iron and is lovely. Both my #102's I've built sound great. First one had Hammond transformers the second one custom made InMadOut.

I'm still not 100% sure what makes an amp great


M

The NOS is Fender from 60s/70s (schumacher) as well.

I am finishing a #124 type amp with a Classic Tone OT, but considering different options as well for the next which is more like a SSS. Options follow:

Older: Vintage or NOS Fender
Newer: Classic Tone, InMadOut

I like the new OTs due to the impedance tap, although I would go older trannies if it makes a big difference soundwise.

[mojotom]

For the record I build two 124 years appart with a NOS OT and a new modern OT (very good brand) and preferred the one with an old OT by far.

The new OT was huge, supposed to be an upgrade but I found it too stiff and a bit sterile compare to the old one.

As I prefer that amp with a mismatch (4R tap to 8R speakers) if I had the choice between the two I would pick the old one and kept a few 60's Deluxe, Bassman and twin OT for those builds.

I have build smaller amps with new transformers (inmadout) with great results too but I like NOS OT as the amp sounds already well broken in from the start and more mellow.

[martin manning]

For the record I build two 124 years appart with a NOS OT and a new modern OT (very good brand) and preferred the one with an old OT by far. The new OT was huge, supposed to be an upgrade but I found it too stiff and a bit sterile compare to the old one.

Was it overpriced too? ;^)
Not to question your judgement, but time (years apart), and any other differences between the two, such as components and speakers might make it hard to say that the improvement was solely due to the OT.

[mojotom]

For the record I build two 124 years appart with a NOS OT and a new modern OT (very good brand) and preferred the one with an old OT by far. The new OT was huge, supposed to be an upgrade but I found it too stiff and a bit sterile compare to the old one.

Was it overpriced too? ;^)
Not to question your judgement, but time (years apart), and any other differences between the two, such as components and speakers might make it hard to say that the improvement was solely due to the OT.

Yes it was
And I did use more "high end" components and shielded wire on that build and came back to more standard stuff except for the precision supply (the first one did use the old style power supply).
Didn't bound with the OD but the clean was full. Couldn't get rid off the stiffness on that build and my take at the time was the "super high-end" OT did not help.

I did build other D style amps with vintage bassman and twin OTs and they have something in common soundwise I didn't found in builds with new OTs (even after few years of use) hence why I picked one here and there for future builds.
I did like some Heyboer OT I tried but if I plan to build a 100W ODS I would choose a vintage OT, just for the added smoothness.