Bandmaster/Pro Reverb OT - will it work in a Deluxe?

[Darkbluemurder]

Suppose I want more headroom from a Deluxe without going to 6L6s (I use JJ 6V6S at the moment which are supposed to be similar to 6L6s and I do not want to put additional heater stress on the PT) would this be a good idea?

From what I remember from the data sheets a Deluxe OT is approx. 8k primary for 2 6V6 into 8 Ohms. Bandmaster/Pro Reverb OT is approx. 4k2 primary for 2 6L6 into 4 Ohms. Using this OT into 8 Ohms would make the primary something like 8k4 which matches the 6V6 pair.

Is my thinking correct? Thank you very much for your input/comments.

BTW: the "Deluxe" is my modded Deluxe Reverb II so no vintage piece will be hacked.

[oldhousescott]

David Allen at allenamps.com has a drop-in replacement DR OT (his model TO30D) that will support 6L6's, so it should give more headroom with 6V6's. Drop-in for a standard DR that is, I'm not sure if it will bolt right up on a DRII.

[Darkbluemurder]

David Allen at allenamps.com has a drop-in replacement DR OT (his model TO30D) that will support 6L6's, so it should give more headroom with 6V6's. Drop-in for a standard DR that is, I'm not sure if it will bolt right up on a DRII.

Thanks, I have seen this. Cool offerings. In fact I thought about acquiring the Allen Pro/Bandmaster upgrade (which is supposed to be more like a Bassman OT) for my Bandmaster and use the Bandmaster OT for the Deluxe Reverb II.

[MarkB]

Your thinking was correct.

[jaysg]

I'm not sure you'll get more headroom...you should get better bass response. You'll probably have a better clean channel cranked tone in the midrange -- my experience replacing a series II OT. [edit] Be prepared to lower the values of the pass caps out of the PI if you replace the OT.

[Darkbluemurder]

I'm not sure you'll get more headroom...you should get better bass response. You'll probably have a better clean channel cranked tone in the midrange -- my experience replacing a series II OT.

Better bass response sure sounds good to me. That's where Deluxes are traditionally weak. Actually the OT in the Deluxe Reverb II isn't original. I replaced the original with a MM a while ago. The difference was not significant IMHO. Maybe a little more detail but not much, and it still is not as strong in the bass as I would like. The MM choke however gave a lot more detail compared to the original DR II choke. The PT is still original.

I once tried 6V6s in my reissue JTM 45 and liked it. What amazed me was that the amp did not get quieter than with the 5881 pair. It was still much louder than the DR II with the same tube type so it must be something else. I suppose a DR OT just gives a lot less power than the JTM 45 OT or a Bandmaster OT.

Since the DR II is now a non-HRM D-clone I am unlikely to crank it in the clean channel.

[mlp-mx6]

I once tried 6V6s in my reissue JTM 45 and liked it. What amazed me was that the amp did not get quieter than with the 5881 pair. It was still much louder than the DR II with the same tube type so it must be something else. I suppose a DR OT just gives a lot less power than the JTM 45 OT or a Bandmaster OT.

Voltage and available current for the JTM power supply would be two factors that would cause you to perceive little-to-no difference. Another factor is the logarithmic relationship between output power and perceived volume. 2X as loud to you is 10X as much power. Twice as loud as a 20W amp requires a 200W amp. The perceived volume difference between a 20W and a 40W amp (especially with the same speaker cab) is not much.

[jaysg]

Actually the OT in the Deluxe Reverb II isn't original. I replaced the original with a MM a while ago. The difference was not significant IMHO. Maybe a little more detail but not much, and it still is not as strong in the bass as I would like. The MM choke however gave a lot more detail compared to the original DR II choke.

Interesting. My experience is with the Concert which had their mid-80's universal OT. It was clearly tweaked to reduce the low end. They used 0.1uF pass caps out of the PI. The choke on it is barely bigger than my thumb. hmm...aquisition therapy time

[Darkbluemurder]

I once tried 6V6s in my reissue JTM 45 and liked it. What amazed me was that the amp did not get quieter than with the 5881 pair. It was still much louder than the DR II with the same tube type so it must be something else. I suppose a DR OT just gives a lot less power than the JTM 45 OT or a Bandmaster OT.

Voltage and available current for the JTM power supply would be two factors that would cause you to perceive little-to-no difference. Another factor is the logarithmic relationship between output power and perceived volume. 2X as loud to you is 10X as much power. Twice as loud as a 20W amp requires a 200W amp. The perceived volume difference between a 20W and a 40W amp (especially with the same speaker cab) is not much.

For what it's worth, B+ on the power tubes is around 400 V in both amps. The difference is that there are twice as many preamp tubes in the DR II.
I know the relationship 2xvolume = 10xpower but the JTM 45 at nominal 30W is way louder than the 20W DR II which should normally be barely audible - given the same plate voltage the OT is a likely suspect.

BTW: can old filter caps reduce volume?

[Darkbluemurder]

Actually the OT in the Deluxe Reverb II isn't original. I replaced the original with a MM a while ago. The difference was not significant IMHO. Maybe a little more detail but not much, and it still is not as strong in the bass as I would like. The MM choke however gave a lot more detail compared to the original DR II choke.

Interesting. My experience is with the Concert which had their mid-80's universal OT. It was clearly tweaked to reduce the low end. They used 0.1uF pass caps out of the PI. The choke on it is barely bigger than my thumb. hmm...aquisition therapy time

Jay,

You are correct. The Concert specs a 022707 choke which is the Deluxe choke! I don't know why Fender did this. I'll probably try a 270 ohms 10W wirewound resistor in its place anyway. You could also be correct on the Concert OT. The PI coupling caps originally were 0.01uF. When I replace 0.022 uF caps with 0.1uf in a Marshall there is a huge increase in low end. Not so in the Concert where I would have expected an even bigger increase going from 0.01uF to 0.1uF. Strange ...

Stephan

[Normster]

I know the relationship 2xvolume = 10xpower but the JTM 45 at nominal 30W is way louder than the 20W DR II which should normally be barely audible - given the same plate voltage the OT is a likely suspect.

I noticed the same thing after building my TW Express a few months ago. Even at 22 watts with 6V6 power tubes, the amp was just incredibly loud...much louder than my 50 watt Dumble. My theory is that it's not wattage that makes an amp sound loud, but the frequency that the wattage is applied to.

The Dumble is more scooped than the TW with much of the power being applied to the lower mids. The TW (and the JTM45) apply more power to the mids and upper mids which the human ear perceives as louder. Add to that the smoothing that Dumble uses via snubbers to tame transient peaks.

In a discussion about Fender versus Marshall, Bunkie (a forum member at jdbluesville who works for Bose) responded to my theory as follows:

You're absolutely right! Low frequencies require more power for a given output level. A "brighter" amp (one with more emphasis on highs) will sound louder. That's probably why the aforementioned Fender is louder than the Marshall...

YMMV

[Darkbluemurder]

I know the relationship 2xvolume = 10xpower but the JTM 45 at nominal 30W is way louder than the 20W DR II which should normally be barely audible - given the same plate voltage the OT is a likely suspect.

I noticed the same thing after building my TW Express a few months ago. Even at 22 watts with 6V6 power tubes, the amp was just incredibly loud...much louder than my 50 watt Dumble. My theory is that it's not wattage that makes an amp sound loud, but the frequency that the wattage is applied to.

The Dumble is more scooped than the TW with much of the power being applied to the lower mids. The TW (and the JTM45) apply more power to the mids and upper mids which the human ear perceives as louder. Add to that the smoothing that Dumble uses via snubbers to tame transient peaks.

Low frequencies require more power for a given output level. A "brighter" amp (one with more emphasis on highs) will sound louder.

YMMV

This is certainly true and probably the reason why the later Marshalls are perceived as being loud as hell because of the upper midrange.

Meanwhile I decided to live with the reduced volume of the DR II. In fact it is still ample volume for my stage uses. With the Concert I have to use the effects loop and turn down the return level knob to control this amp.