Tube rolling on Foreplay III

[Anton]

Hello,
Does anybody have experience with tubes rolling on Foreplay III? Any recommendations on replacement for stock 12AU7 and what difference does it make?
I just finished my Foreplay III couple of weeks ago and breaking-in it now. I am not going to upgrade anything right away - want to give it enough time to fully break-in before start tweaking it.
Following the advise from Grainger I am going to replace stock capacitors for Teflon ones (I have some Soviet Teflon caps) and was wondering what I could improve in terms of tubes.
Will appreciate any good advise. Thanks

[Lee Hankins]

Anton, It has been years since I did any tube rolling in my Extended FPIII, but here are the tubes than I ended up with.  I changed the octal 0D3 shunt regulator socket to a 9 pin socket, and a Sylvania 6DJ8 is in this position.  I have 40+ tubes in the 6DJ8/6922 family and usually do extensive tube rolling so I have to assume that this Sylvania tube sound best in the shunt regulator position.  In place of the 12AU7 tube I have two Phillips Military D2540 CCA's, this is a premium 6922 tube.  I must like the sound of a 6DJ8 better than a 12AU7 (I also have a large quantity of 12AU7's for tube rolling).

Hope that this little trip down memory lane is of some help to you.

Cordially,
Lee Hankins

[Grainger49]

I made a list of FP 1 & 2 tube equivalents.  (all are applicable to the FP III)  Here is the thread:

http://www.bottlehead.com/smf/index.php/topic,1027.0.html

My favorites have been 60s or 70s JAN Sylvania 6189.

One of the major upgrades with the FP III was that it could supply the voltage and current needed for a number of other tubes.  The 6SN7 is one that was often asked for.  Poster "Paully" converted his to the 7N7 which is a 6SN7 in Loctal rather than Octal form.  The good thing here is that it is much cheaper than vintage 6SN7s.  I can supply the tube pin changes.

[hennfarm]

try some 5814a grey or blackplates. i moved heater wires and currently run 6/8gc7 

[Deafer_than_a_doornail]

This thread is a little confusing to me. I just got my kit and haven't started building it yet, but hope to try some different tubes when it is finished. What is confusing is that someone mentioned using 6922 tubes, while those are not on Granger's list.

Are 6922's directly swappable, are they equivalent, or does it involve some circuit modification?

I ask because I already have several different matched pairs of 6922's and 7308's from various manufacturers, some of which are costly, for rolling in a tubed CD player, and it would be nice if I can also try those in my Foreplay III.

[Grainger49]

The 6922 is a 6DJ8 (6.3V) variant.  The FP III is wired for a 12AU7 (12.6V), so the heater wires are wrong to begin with.  The pin outs, meaning what is attached to all the pins, are the same except the 6DJ8 doesn't have a center lead to the heater like the 12AU7.

If you drop a 6922 into the FP III it will not work since the heater is not wired up. 

[Paully]

I think he was saying that he changed the OD3 regulator to a 6DJ8 and it has nothing to do with the 12au7 tubes, if I am reading it correctly.

Two suggestions for tube swapping.  Try some Mullard CV4003, a pernnial favorite, tried and true.  There are better but it seems they are some of the best tubes you can still buy for a reasonable price.  When I put a pair in My FPII I stopped rolling and they also sound incredible in my FPIII.  Upscale Audio has some for about $60 a pair, which is about what you would expect to pay for some tested and selected tubes from a reputable dealer.

Second, when you get feeling reeling rowdy, convert your amp to 6SN7 and have some fun with that!

[Grainger49]

Of course I'm not familiar with the extended version.  If that is what he is saying then I can't help at all.

Edit: I looked, the Extended uses a third 12AU7 but not a 6DJ8/6922 variant.  There is still a heater problem and probably more problems.

[Paul Joppa]

The 6922 is not a 12AU7 equivalent. It should work (have about the right voltages) in the Foreplay III if you re-wire the heaters - that's just a lucky coincidence though; in general they are not compatible. The 6922 will have twice the gain, and Foreplay already has plenty of gain. I would probably advise adding plate stoppers as well as being extra careful with installation of the grid stoppers.

A much better thing to do with premium 6922s (and 7308s) is to use them in the Seduction phono preamp, if you have one.

[patm]

I agree with poster Paully. I got a pair of cv4003's from Upscale and they are sweet. The tubes I replaced were used Amperex, no match for the Mullards (cv4003).

Pat

[Deafer_than_a_doornail]

Thanks all. This is clear now. I'll look for some Mullard cv4003's here (Japan) or order them from Upscale in the US if can't find them here. I got most of my other tubes from Upscale in the past.  In the meantime I found some Matsushita 12AU7/ECC82's here, which I've read were made for Phillips/Mullard, and also some by Toshiba, both matched pairs and not too costly, which I can try out.

New question: Does the center 12UA7 in the Extended FP III need to be matched with the other two?

[Paul Joppa]

The center tube in an Extended Foreplay III is the shunt regulator, and it has much less influence - the shunt reg chip controls the tube very tightly.

[Deafer_than_a_doornail]

Thanks, Paul

To me it's a little too bad the center tube needed changing for the upgrade, in terms of looks. I really like the classic look of that old RCA OD3, but this thing is supposed to be heard rather than seen, I suppose.

I can't wait to start building my kit, which hopefully can commence next week...

[Paul Joppa]

We don't offer a partial kit, but you can leave out the hybrid shunt reg and keep the 0D3 if you want. It's not as good, but others have done this. They ARE pretty!

[Lee Hankins]

Pauls remarks about the 6922 has made me sort of nervous in their use in my FPIII, even though they sound very good and have been in the FPIII for over a year without any problems.  Like Paul I am a fan of the 6SN7 tube, so I replaced the 6DJ8 and the 6922 with a RCA 6CG7 and RCA clear top 6FQ7's.  Much better sounding than the 6DJ8 family in the FPIII, highly recommended.  Excellent match with the soft start Paramounts.

Lee Hankins