Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: Anton on December 16, 2010, 03:10:56 PM
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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
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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
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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.
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try some 5814a grey or blackplates. i moved heater wires and currently run 6/8gc7
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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.
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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.
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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!
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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.
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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.
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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
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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?
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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.
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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...
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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!
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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
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Anton
I replaced the stock EH 12au7's with NOS RCA clear top 12au7's. It made a noticeable improvement in the sound quality.
Debra
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Thanks everybody for recommendations.
I just finished extended upgrade for my Foreplay III.
I am currently using JAN Sylvania 6189 for output tubes, which were a replacement for stock 12AU7s. To be honest I didn't hear a lot of difference sound wise.
I decided to follow Paully's advise and ordered a matched pair of Mullard CV4003 from Upscale Audio. Not cheap actually ))) so I hope I am gonna like it.
Although to be honest - it sounds very good the way it is right now)))
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Make sure you post back what you think (even if you don't like them, won't hurt my feelings!). I will be curious to know. And you can get some more recommendations if you need them. I think you will be quite happy once they break in. 20 hours should be plenty.
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i just did some work on my foreplay III- put obbligato 4.7's premiums and put some mazda cifte 12au7
it sounds quite nice -especially since i am driving a a SS mcintosh mc250--i have ordered some obbligato PIO caps to give them a try as grainger highly recommends them
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here is the update...
I am using Mullard CV 4003 for almost 3 weeks now. Think it was long enough for tubes to break-in.
I like the sound, but honestly speaking I don't hear much difference from stock 12AU7 and JAN Sylvania 6189 I was using before. I came to conclusion that my ears are not that sensitive to capture all these nuances. I guess it is just the way I am, and I accepted the fact that I am not one of those guys who can write page-long vacuum tube review )))
but that doesn't prevent me from enjoying my favorite music on a gear I assembled with my own hands - and that's all what matters )))
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Nothing wrong with liking cheaper tubes! They're cheaper!
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Hi All!
Can I use a pair of Philips E80CC's in my Foreplay?
Here's the datasheet:
http://www.hifitubes.nl/weblog/index.php/philips-e80cc-datasheet/
I see both "12.6" and "6.3" volts for heater voltages, and I'm not sure which applies.
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Hi All!
Can I use a pair of Philips E80CC's in my Foreplay?
Possibly. Look at the curves, for 75v on the plate and 3.6mA current. If the bias is close to 1.57 volts, then it should bias up properly. This appears to be the case. Note that the gain will be higher - 27/17 or about 4dB.
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This link is not in the FP III folder but anything that could work with the 1 and 2 will work in the III, plus more. Every number listed will be a drop in replacement unless it says different.
http://www.bottlehead.com/smf/index.php/topic,1027.0.html
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Thanks Paul, Granger!
The E80CC is not on the "drop-in" list - would it require some circuit modification for the FP III?
How about for the Extended upgrade?
I also wonder- for the Extended upgrade, should I be looking at matched sets of 3 tubes, or is it ok if the middle regulator tube is not matched with the other two?
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Been using Psvane 12au7. I think it is a noticeable improvement over the RCA clear tops i was using before.
Deb
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Deafer_than_a_doornail,
No, I'm pretty sure that is an oversight on my part. The E80CC should be on my master list and didn't get transferred to the post. I will add it.
Edit: The heater current is twice what a FP 1 or 2 can deliver. It is just fine for the FP III. So it doesn't belong on the FP 1 & 2 list but would be on a FP III list.
Thanks!
Extending makes no difference in the tubes. It does set the current. Unless you get more creative with tubes, changing the operating point and tube you don't need to adjust the current from the C4S boards.
I don't match preamp tubes. Some do, I don't. The VR tube needs not be matched to anything. As long as that one is working you are good.
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I would stay with a 12AU7 or equivalent for the center (shunt regulator) tube on the Foreplay III. You do not want the cathode voltage to drop below 2.5v, because then the 431 chip would not regulate.
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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!
I just received the extended kit and want to keep the OD3 tube for the time being and put in the 12AU7 later.. I'm not very good at understanding the electrical prints so what I'm asking is there anything I should be concerned about by leaving it in? I'm already stumped on the taking all the stuff out in the beginning of the kit right away... is there a simple diagram somewhere on how to do this. Or should I just install the 12AU7 because its such an improvement I'd be an idiot not to do it?
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The community suggests you build stock, not extended, first. Then after becoming used to the stock sound you add the Extended kit and know what changes it brings.
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Grainger, I think Helmut already has the FPIII up and running in stock form. I cant offer him advice for his question (sorry Helmut) but just wanted to help clairfy what he was asking.
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I had been running a pair of nice RCA Cleartops for a year before recently trying a pair of Tung Sol Blackglass versions. Like 'em a lot. Highs almost identicle to the RCAs, but much more solid bottom end.
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I do have the stock Foreplay III built and am using a matched set of Cleartops in it. The extended will get built in the next few weeks and I will do the full kit. I really like the looks of the 0D3 (I'd like to keep it) and I'm almost sure I wouldn't hear the difference between that and the 12AU7 but anyway...
I use the Foreplay more as a variable voltage or gain connecting box so I don't have to switch wires to use either of my 3 headphone amps. A music loving friend said that using a preamp before an amp with a volume control is degrading the sound and I would be better off taking the Goldpoints out of the Beta 22 & Bijou and use the Foreplay to control the volume. Makes sense but as I have now it sounds OK to me and the Foreplay only has 11 steps with the Sweet Whispers. Now comes the question...
Keeping as I have it now what is the proper way to adjust the volume controls? The 3 headphone amps have different gains and the 4 headphones have different Ohm levels so, for example, I use the Foreplay to to make the input voltage hotter or colder on the Beta 22 (2X gain) when each headphone is used. I built the Beta 22 to match perfectly with the 25 Ohm Denon 7000's but it don't go loud enough with the STAX SRD-7 SB transformer box (the SEX 2.1 amp will be used for this purpose when BH has the trans switching board for sale). So I "feed" it more from the Foreplay and that decreases the travel of the volume control on the B22 and I turn it up so the STAX 'phones are at the loudness I like. Is this damaging anything? No problems so far the last couple of months. Have the X-FI set at maximum because it's a software volume control so I know I have that right. I adjust the Foreplay to suit my other amps likewise so the volume is at 12 o'clock or so with whatever 'phones I use. In theory is this just plain wrong and I am really missing something in SQ or don't worry be happy...
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To my mind, optimizing the signal voltage level in each component is far more important than any degradation from an extra level control. See my white paper on the Bottlehead - Community page.
Depending on the voltage from the source, use the Foreplay's input resistor to set the Foreplay gain for a substantial output at maximum volume; I'd suggest 2 to 8 volts full scale (the way digital devices are usually specified). Then set the headphone amp's gain so that produces the most loudness you'd ever want. Now you can leave the head amp's control alone, and use the Foreplay controls, whose range is adequate because you are using their whole range, not just the first 20% of it.