Reverb Pan Impedance Question

[Pryde]

I am looking into building a Princeton Reverb circuit and already have a custom combo cab I want to use. However, it is not wide enough to house a 16.75" long tank (4AB3C1B)

I do see there is a 8AB3C1B pan (only 9" long) that would easily fit in the cab BUT the input/output impedance is a little different between the two:

4AB3C1B has 8-ohm input and 2250-ohm output
8AB3C1B as 10-ohm input and 2575-ohm output

Any issues with using the smaller tank in a Princeton reverb circuit?

I appreciate the help

[g1]

The impedance differences are too slight to be noticeable.
The only drawback to using the short tank is that only a long tank sounds as good as a long tank.
Some people won't notice the difference, some will find it quite noticeable.

[mhuss]

The only drawback to using the short tank is that only a long tank sounds as good as a long tank.
Some people won't notice the difference, some will find it quite noticeable.

This.

[Enzo]

That is like a 10% difference, and as was said above, you'd never notice.

One thing to always remember when working with guitar amps: they are just guitar amps, not some NASA space probe laboratory thing. They are not precision instruments, and there is nothing in them that is so critical as to warranty 1% tolerances. Look at the note #1 in the upper right of the schematic I link here. It says voltages ought to be within 20%. That is how precise this stuff is.

http://bmamps.com/Schematics/fender/...b763_schem.pdf

[Chuck H]

It's true that only the long tank sounds like the long tank. But they don't sound like they use to anyway. Much more one dimensional. And it's nearly always a two row long tank that's OEM. IMHE the modern short three row tanks sound just as good as the modern long two row tanks.

I've done instant swap tests with both the tanks you propose. Electronically there is no problem and audibly there is no notable difference in volume.

[Pryde]

Good to know guys thank you. I am not after big-surfy reverb, rather I just use a touch of it so the smaller tank should suffice well for me.

[uneumann]

It's true that only the long tank sounds like the long tank. But they don't sound like they use to anyway. Much more one dimensional. And it's nearly always a two row long tank that's OEM. IMHE the modern short three row tanks sound just as good as the modern long two row tanks.

I've done instant swap tests with both the tanks you propose. Electronically there is no problem and audibly there is no notable difference in volume.

Ditto. I recently compared a full-length 2-spring pan from DR clone to a short 3-spring MOD 8AB2A1B pan. Very comparable results. I could even talk myself into favoring the short pan as a bit less-mushy at the bottom end.

[Enzo]

The large pan is not so much about being surfy, as it is to just not sound spoingy like a screen door spring. That is why there are two or three springs, and in fact the older pans had long spring which were made of two half-length springs of different pitch joined in the center. All just to make the reverb sound more complex. In other words it is the quality of the sound, not the amount of it.

[Chuck H]

The large pan is not so much about being surfy, as it is to just not sound spoingy like a screen door spring. That is why there are two or three springs, and in fact the older pans had long spring which were made of two half-length springs of different pitch joined in the center. All just to make the reverb sound more complex. In other words it is the quality of the sound, not the amount of it.

+1
I think that may be why, with newer pans anyway, the three row short tank sounds as good as the two row long tank. I don't think the two rows on the long tanks are set up as well or carefully as they might have been in the olden days. I knew that the series springs on the older long tanks were asymmetrical. I'm not sure that's being done as well (or at all) anymore. So three differentiated single springs comes off sounding pretty good by comparison.

[Enzo]

It may be my imagination, but I detect a difference in sound with the shorter pans. I write it off to the shorter spring's lack of length to allow reverb sounds to develop more. The signal in the long pan goes four times as far before the reflection hits the drive. Like the difference between echo and slapback.

[Chuck H]

Yup. I hear that difference too. Even in the new tanks. But with the series spring differential being done less carefully you end up with more phase cancellations at the end of the "whisper game" chain. I notice a lot more representation of the original signal at the output transducers in the new long tanks compared to vintage tanks. And I think that somewhat confirms my suspicions. Having more time delay version of the original signal show up at the reverb output also interacts with the dry signal more. Also phase dependent. This could also be part of why new tanks seem more microphonic. Then there's the spring steel quality. China doesn't exactly have a reputation for quality steels. Not that they can't do it. But it's expensive and doesn't correlate with building to the lowest acceptable spec. that makes their customers bottom line look better. I've sort of given up on the new long tanks after having to toss four out of the last five purchased and replacing them with short tanks. Even then, it can be a real struggle to stabilize them in combo amps. Impossible with the long new tanks.

[Mick Bailey]

Then there are the short pans that are actually long..... the Wisconsin Cascade units. They have four springs of different pitch and opposite wind direction, with a pair of diagonally opposed transducers. There's a suspension point opposite each transducer and each point is linked by a single strand of thin spring wire. They also usually have a cap across the output to enhance the resonant frequency.

The total folded spring length comes to around 14".

[Chuck H]

Then there are the short pans that are actually long..... the Wisconsin Cascade units. They have four springs of different pitch and opposite wind direction, with a pair of diagonally opposed transducers. There's a suspension point opposite each transducer and each point is linked by a single strand of thin spring wire. They also usually have a cap across the output to enhance the resonant frequency.

The total folded spring length comes to around 14".

I'm going to need a link. I don't know those tanks, but I'm intrigued.

[Enzo]

Is that the old OC unit, the one made by pretty girls etc?

[nsubulysses]

Found in Sunns and what else? Probably many things, those tanks made by pretty girls in Wisconsin