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I'm trying to figure out the originally-spec'd tubes for two different pairs of Don Allen single-ended mono amps. I'm not the original owner, and everyone associated has left us for a better place. So, maybe someone still around can help?- First pair came to me with 801A outputs, but I'm assuming the 10 would also be kosher?
- Same amps came with 6BC8 drivers - are those likely original? (I've seen mentions here of Don's specifying those at times.)
- Second pair (with 45 outputs) came with Japanese 6AQ8/ECC85 drivers. Are those liable to be original - or were they more likely 6BQ7?
- Same amps came with 6X5 rectifiers, but I can't find any mention of Don's having used those. Thoughts?
- While I'm at it, might as well ask whether 6N1P is OK in Don's 2-tube preamp? (If I've identified the power transformer correctly, I think the pair of 6N1Ps draws more than the PT's rated current. I don't detect it running hotter than with 6BQ7s, though - and 6N1Ps have been in use for 6-8 mos. Not sure where that leaves things.)
6N1P is also great in the 45 monos (but not as good in the 801A monos). Any other recommended drivers for these guys?
I know this may all be a long-shot ... but if not here, then where?
Thanks!
Edits: 11/03/21Follow Ups:
Lord have mercy!
The Don Allen Preamp and Larry Moore Ultra Fi look very familiar!
What a great set-up and I wish I could teleport to NYC for a listen.
Will
"I'm trying to figure out the originally-spec'd tubes for two different pairs of Don Allen single-ended mono amps. I'm not the original owner, and everyone associated has left us for a better place. So, maybe someone still around can help?"
I'll try..... I'll be using his amplifiers as long as I'm walking the planet......
"- First pair came to me with 801A outputs, but I'm assuming the 10 would also be kosher?"
Yes..... 801, 801A, 10, or VT25 will work..... There are other equivalents that escape me, for the moment.
"- Same amps came with 6BC8 drivers - are those likely original? (I've seen mentions here of Don's specifying those at times.)"
This is a 6BQ7 variant..... Don's tube of choice is the GE 6BQ7A..... Be sure they're not "rebadged" 6BZ7s, which to me don't quite sound as good.
There are a lot of variants for this tube, it can turn into a tube-rolling bonanza..... 6BS8 and 6BZ8 also work..... At least these variants are not overly expensive, and readily available on eBay. (I'd go with Jim McShane personally.)
"- Second pair (with 45 outputs) came with Japanese 6AQ8/ECC85 drivers. Are those liable to be original - or were they more likely 6BQ7?"
Once again, Don's tube of choice for the driver is the GE 6BQ7A. (He used this tube exclusively in all of his gear, even though a lot of variants can be used.)
"- Same amps came with 6X5 rectifiers, but I can't find any mention of Don's having used those. Thoughts?"
I've never seen a Don Allen amplifier with a 6X5 rectifier.... I wouldn't mess with the rectifier until someone chimes in who is familiar with it.
"- While I'm at it, might as well ask whether 6N1P is OK in Don's 2-tube preamp? (If I've identified the power transformer correctly, I think the pair of 6N1Ps draws more than the PT's rated current. I don't detect it running hotter than with 6BQ7s, though - and 6N1Ps have been in use for 6-8 mos. Not sure where that leaves things.)"
I've never tried 6N1Ps in Don's gear.... The only Russian substitute that I know works in his gear is the 6N23P...... (Although I don't like them in the line stage. I like Philips 6DJ8s in his line stage.)
"6N1P is also great in the 45 monos (but not as good in the 801A monos). Any other recommended drivers for these guys?"
I like the new production Genelex 6922 in the 10/801A amps.... (I'm currently running a stereo amp with these tubes.)
I use RCA 6BK7B in my Don Allen 45 amp. (I rotate both the 10 and 45 amps in the high-efficiency system..... )
"I know this may all be a long-shot ... but if not here, then where?"
Feel free to ask more questions..... These amps are amazing when matched with your speakers and source gear. What you end up using/liking might not be the same tubes as what I use for my systems.
I was hoping you'd be along with all the insight, Todd. Thanks so much. Meanwhile, sorry for the delayed response. I definitely needed some time to absorb all these ideas.I'll try..... I'll be using his amplifiers as long as I'm walking the planet......
My lord, these amplifiers are wonderful.
In addition to the 45 and 10/801 monos that I asked about, I have a stereo 807, too. It's configured differently than others I've seen: 1/2 6SN7 (with "starved" 5.5VDC filament) > > > 6J5 > > > 807 (pentode wired), plus 2 x OC3 and 2 x OD3 regulators. I'm currently using all the amps in rotation in a multi-amped horn system. (I'll drop a few photos at the end.)
Yes..... 801, 801A, 10, or VT25 will work..... There are other equivalents that escape me, for the moment.
I'd really like to try the graphite-plate RCA 801. I've been searching, but it's a tough find at a realistic price. (Leads from anyone would be welcome.)
BTW, elsewhere in this thread, Cleantimestream mentioned the 10's lower (500VDC) max plate voltage. So, I measured: 450-460VDC on mine. With that, I started to wonder if the 10 may have been Don's preference (over the 801/A). Any insight?
[6BC8] is a 6BQ7 variant..... Don's tube of choice is the GE 6BQ7A..... Be sure they're not "rebadged" 6BZ7s, which to me don't quite sound as good.
There are a lot of variants for this tube, it can turn into a tube-rolling bonanza..... 6BS8 and 6BZ8 also work..... At least these variants are not overly expensive, and readily available on eBay. (I'd go with Jim McShane personally.)
I do have some Don-supplied GE 6BQ7As, and I picked up a bunch of Tektronix GEs when I got my first preamp. I should be in good shape.
Once again, Don's tube of choice for the driver is the GE 6BQ7A. (He used this tube exclusively in all of his gear, even though a lot of variants can be used.)
This was the definitive statement I was looking for. If all the noval-driver amps were born with a GE 6BQ7A, then I know where baseline is.
I've never seen a Don Allen amplifier with a 6X5 rectifier.... I wouldn't mess with the rectifier until someone chimes in who is familiar with it.
I don't think the prior owner* was overly experimental or risk-loving. If he used 6X5, I'm assuming it was originally (even if uniquely) spec'd ... or he got Don's blessing. In addition, the 33uF reservoir capacitor provides extra support for the 6X5's being original.
The only rectifier experiment I've done is with the 6X5-like Bendix 5852. It draws twice the 6X5's filament current from the 6.3V winding, so I've been keeping an infrared thermometer on the power transformer. External surface temp has risen from 105 to 125 deg F in operation. Not alarming -- it's still very "touchable" -- but I'll measure secondary voltages now and be prepared to replace the PTs at some point. I think the improvement in sound quality is worth the risk (if any).
BTW, in my version of the 45 amp, driver is AC-heated with tube-rectified B+ -- while 45 is DC-heated and entirely solid state-rectified. Curious if that was the typical configuration?
I've never tried 6N1Ps in Don's gear.... The only Russian substitute that I know works in his gear is the 6N23P...... (Although I don't like them in the line stage. I like Philips 6DJ8s in his line stage.)
I saw a preamp sell (but not to me) with 6N1Ps, which is what inspired the idea. Elsewhere in this thread, though, Paul Joppa convincingly said that's way off.
Meanwhile, this issue is probably moot. With your 6DJ8 recommendation, and having some Siemens ECC88 on hand, I gave those a try this week. Wow -- they do some very nice things! Bigger and bolder than any alternative I've tried. (And in a small space like mine, I try to grab all the big and bold I can get.) Thanks for the tip! If you wouldn't mind sharing, is there a specific Philips 6DJ8 you look for?
I like the new production Genelex 6922 in the 10/801A amps.... (I'm currently running a stereo amp with these tubes.)
The only 6922s I have on hand are 20-year-old Sovteks, which I haven't tried in the 10/801 yet. I'll do that when the 45 gets a break and the 10/801 takes over. Should I expect a likeness between them and current Genelex -- or a considerable difference?
I use RCA 6BK7B in my Don Allen 45 amp. (I rotate both the 10 and 45 amps in the high-efficiency system..... )
I ordered a handful of RCA 6BK7B (cheap experiment!) and they arrived last weekend. Tried them, but only briefly. Amperex Holland 6AQ8 has been my favorite in the 45 so far, even though its higher gain makes the amp slightly noisy. (At least I think this is the cause.) 6BK7B is more reserved-sounding, but it does make the 45 amp (on HF channel) a more coherent match with the 807 amp (on LF channel). Does 6BK7B open up over time?
BTW, as I wondered about driver options for the 45, I measured plate voltages: 155-165VDC on one plate, 205-215VDC on the other. So, way beyond 6DJ8 specs (which you probably knew already, but just in case).
Feel free to ask more questions..... These amps are amazing when matched with your speakers and source gear. What you end up using/liking might not be the same tubes as what I use for my systems.
I've already asked a bunch of questions above, obviously. And please don't feel compelled to answer all. But, I'm not one to decline an invitation, so...
- Curious what preamp output coupling caps you ended up with -- make, model, capacitance value? (And what were the decision parameters?)
- Could you run down the preamp "taxonomy" (Gen I, Gen II, etc)? I believe I've seen 1, 2, and 4-tube versions.
- Sticking with the preamp, am I right in thinking the 1-tube version provided just voltage gain (and high output impedance); the 2-tube version added a cathode-follower stage (for lower output impedance); and the 4-tube version dual-mono'd the 2-tube concept?
- Any advice on the tube-modded Magnavox CDC 745 CD changer? (Like with the 45 monos, Amperex Holland 6AQ8 has been excellent. But, it looks like your favorite tube is 6N23P.)
- (*Footnoted from above): I'm pretty sure you were acquainted in real life with the original owner of my 45, 10/801, preamp, and CD changer. (All of this gear came from his estate by way of his nephew.) Mind if I send you a PM about that?
As mentioned, a few photos of where things currently stand...
Edits: 11/26/21
Just saw the photos. Very nice. I had a Don Allen 45. It was nice. Nice guy too.
The amp at the lower right looks intriguing, even though it is not Don Allen...... I would be interested in an SET amp with a little extra power.
To answer your questions......
"- Curious what preamp output coupling caps you ended up with -- make, model, capacitance value? (And what were the decision parameters?)"
Use Jupiter Copper Paper-In-Wax in the main system line stage..... Use V-Cap ODAM with 0.01uF bypass caps in the high-efficiency system. Both work to great effect.
"- Could you run down the preamp 'taxonomy' (Gen I, Gen II, etc)? I believe I've seen 1, 2, and 4-tube versions."
That's basically it.... 1, 2, and 4-tube versions.....
"- Sticking with the preamp, am I right in thinking the 1-tube version provided just voltage gain (and high output impedance); the 2-tube version added a cathode-follower stage (for lower output impedance); and the 4-tube version dual-mono'd the 2-tube concept?"
I don't know if some of the 2-tube versions are also dual-mono.... The 4-tube version runs one internal plate of a tube in one channel, the other internal place of another tube the other channel..... So if you have a tube in which one of its two internal triodes has gone bad (for example) in the left channel, you can still use the good triode in the right channel.
"- Any advice on the tube-modded Magnavox CDC 745 CD changer? (Like with the 45 monos, Amperex Holland 6AQ8 has been excellent. But, it looks like your favorite tube is 6N23P.)"
Don modified a lot of Philips/Magnavox/Marantz CD changes, which all had the Philips mechanism...... But the one that really stands out is the Philips CDC-935..... (If this changer had a better stock analog output stage, this could have been a cult classic.) The 935's transport and DAC are both exceptional, put in a good tube output stage, it would compete against just about anything. (I will be doing a shootout with the Gustard X26 Pro external DAC in the not-too-distant future.)
The 1975 Voskhod 6N23P works great with these modified CD changers.
"- (*Footnoted from above): I'm pretty sure you were acquainted in real life with the original owner of my 45, 10/801, preamp, and CD changer. (All of this gear came from his estate by way of his nephew.) Mind if I send you a PM about that?"
Never an issue.... Go ahead..... (My problem is I often miss these things, I get tons of spam.)
".... The only Russian substitute that I know works in his gear is the 6N23P...... (Although I don't like them in the line stage. I like Philips 6DJ8s in his line stage.) ...."The 6N1P is a fine sounding tube, but it is much different from the 6DJ8/6922/6N23P. The plate resistance for instance is 11 Kohms, vs. 2.7 Kohms. The old but widely distributed Svetlana data sheet is incorrect.
[edit 11/5/21 3:30PM to add quotation marks.)
Edits: 11/05/21 11/05/21
"First pair came to me with 801A outputs, but I'm assuming the 10 would also be kosher?" A thoriated tungsten 10 can handle 500 volts {not a lot of those around} An 801A can handle 600 volts on the plate. Schematic would be vital to give an informed valid statement, although most 801A's are being run @ 380 to 450 yielding around 2.5 to 3 watts. Max is 3.8 volts if A2 is not being utilized. Again, would need a schematic. Perhaps those here whom have measured Hogan's work can weigh in?
The Mind has No Firewall~ U.S. Army War College.
Thanks -- appreciate it! On my amps, I measured 450-460VDC (plate to cathode). With that, I started to wonder if the 10 may have been Don Allen's preference. But, you mentioned that even 801A is typically run in this range. How come?
I run my 801A's to obtain approximately 3 watts... for that extra .8 watt you are @ maximum dissipation. Although I have around 75 801's, I see no need to run them at the ragged edge for a minuscule amount more of power.
The 10/10y is slightly warmer than the 801a and cannot handle the same max dissipation. 10 and 801A are only tubes I consider to sound better than the 45...next in line is THE best Push/Pull tube...2A3.
The Mind has No Firewall~ U.S. Army War College.
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