I have a Pilot amp from an old console. I recapped it quite a few years ago but only been using it a year or so. It sounds fine to me (76 yo ears with hearing aids). However, I'm sure I used cheap caps and I put JJ tubes in it. Are there specific places where really good caps would make a difference? Also, what tubes could I try.
A friend and I are planning to diagnose it soon. He just got an oscilloscope and signal generator. Then I think I should transfer it to a better-looking box. So, while I'm doing that, I may consider some changes.
A friend and I are planning to diagnose it soon. He just got an oscilloscope and signal generator. Then I think I should transfer it to a better-looking box. So, while I'm doing that, I may consider some changes.
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Keep it original, and build something else new!
No, I wouldn't bother with that as long as you used decent basic film caps.
If the schematic I found is correct, this uses several decoupling caps between 0.047 and 0.1uF. All these will have a sonic impact BUT the effect maybe somewhat diluted and a recapping to improve sonics maybe an expensive endeavor.
Not sure that the 'keep it original' argument holds since it's already recapped.
If you have used good, reliable Illinois Capacitors level caps I'd leave it alone.
Not sure that the 'keep it original' argument holds since it's already recapped.
If you have used good, reliable Illinois Capacitors level caps I'd leave it alone.
You did not mention replacing the electrolytic capacitors. Judging from looks it appears you still have the original can capacitors. If you don’t experience hum or overheating of these capacitors now they can live/serve for a while. But eventually you will need to replace them. And since you are working on it shortly I would recommend replacing all the electrolytic caps now that you have not already replaced.
Your tubes are probably good if they test strong. What 12ax7s are you using? Investing in the best 12ax7s that you can afford will pay off in this location. JJ EL84 tubes are fine if you buy them tested. JJ rectifiers do not have a good reputation, but I see you have a nice Tungsol made in Russia GZ34 installed that should be good for many more years.
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If you still use original electrolytic caps and they are measuring good, it is good. If you use modern caps, especially mounted on their leads, they will dry fast. Modern caps have leads going all the way through rubber seal, riveted to very thin foil. Heated up they expel some electrolyte, cooling down they suck in some air, and so on...
In good vintage caps (and expensive new caps) external and internal leads are mechanically separated through hard dielectric plate, so stress on leads caused by vibrations and accelerations do not tear off riveting from the foil.
When I see picture of boutique amps underneath, that cause audiophiles to drool, I see massive caps hanging on thin leads, and it causes a feeling of sand paper on my tongue...
Here is a new Nichicon cap mounted on PCB without mechanical fixation of it's body.
In good vintage caps (and expensive new caps) external and internal leads are mechanically separated through hard dielectric plate, so stress on leads caused by vibrations and accelerations do not tear off riveting from the foil.
When I see picture of boutique amps underneath, that cause audiophiles to drool, I see massive caps hanging on thin leads, and it causes a feeling of sand paper on my tongue...
Here is a new Nichicon cap mounted on PCB without mechanical fixation of it's body.
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I used MIEC electrolytic caps (black and silver things) soldered under the chassis. The symbol keys told me what went where on those. Really knew nothing at the time (still don't) just bought what I could find that matched the parts list. Used red-dips for many of the smaller caps. Do still have the capacitors I removed. Maybe I should test them.
Would you consider MIEC a good cap? I'm guessing not as the most expensive was prb $5 and they are just hanging on their leads. Not that many hours on this amp so far, though.
Possibly. But not nearly as much difference as optimizing your speakers.
Speakers are 90% of an amplifier's sound. Before tinkering with things like capacitors and resistors, make sure that the speakers you are using are a good match to the amplifier and are of the highest performance you can afford. Once that's done, you can tinker with the amplifier.
Just my opinion. Sure other people have their own. YMMV
I have not personally used MIEC capacitors, but they have a good reputation among the justradios.com crowd. Regarding 12ax7s, if I were in your shoes I would keep using my JJs and buy a good set of tubes as back up if and when you encounter a good deal. Taste in 12ax7s is a personal thing. I like Telefunken ECC83 but acquired them years ago before their prices got out of reach. Most NOS American and Western European 12ax7/ECC83 are very good and last a long time, so used ones are a definite option. I have not used JJ 12ax7, but have heard good things about their small signal tubes and several power tubes. Some user say they like JJ as well as NOS American.
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Considering changing driver tubes. Most new (Gold Lion, Mullard, Tungsol) are made in Russia, which I don't want to support. Sorry Saratovians, talk to your fearless leader. Telefunken are now made in Slovakia and are part of JJ. JJ looks to have some premium lines. NOS 12AX7s are around 120/ea but NOS 12AT7s are very reasonable. I was thinking of a matched pair of NOS Phillips 12AT7WC (joint army-navy). To me they look better than the NOS Mullard 12AT7s.
I have a very budget system w/ used and vintage components. I have about $350-$400 in the Thorens TD125 MkII (interesting story there), $130 for an NAD 3130, $80 for Boston Acoustic A70s, and less than $100 into the Pilot. A furniture rearrangement made it necc to get high frequencies above the back of a sofa so I needed bookshelf speakers. The 2nd pair I tried are Linn Majik 109s, 20 yrs old for $600. The Linns are 4 OHM so are driven by the NAD in 4 OHM mode. The Pilot drives the 90 Db A70s. It sounds better than one would think. Upgrading the A70s is a thought but if I had something like B&W bookshelves I might not need the floor speakers. Very nice highs from the Linns, though. Another tube amp tapped for 4 OHM would be nice.
Looked at CE manufacturing. Very nice, using old Mallory equipment. Clicked on where to buy and went to CE Distribution. Started an account until I got to proof of business to verify that I was not buying their products for personal use. I do see some distributors and multiple EBay hits. I will get those and redo parts of the amp. Thanks.
The 12AT7 is not a drop in substitute for the 12AX7 used in the Pilot. They have the same pinout but operating points are different. The various JJ 12AX7 varieties (12AX7, ECC803, E83CC, 7025) seem to have a very good reputation if you just want to try something different. The 5751 will also work if you want something with a bit less gain. Antique Electronics (tubesandmore.com) is a good source if you're in the U.S.
If you previously replaced the electrolytic can caps with individual caps mounted inside the chassis I wouldn’t bother replacing them again unless there is some indication that they are failing. Replacement cans are very expensive compared to individual caps. To me, they only make sense if there is no way to fit individual caps underneath.
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If you change the driver/phase splitter tube from a 12ax7 to a12at7 you have a different amp that may of may not sound good. Your amp is optimized for 12AX7 so if you can afford it stay with 12ax7s.
However, if you need to rebuild the amp (replace resistors and caps you have not changed yet) you could rebuild it to suit a different front tube, such as 12AT7 you suggested. Tubelab has a design, called SPP (Simple Push-Pull) that sounds good and works well with 12AT7. I don’t know the details of your amp (B+, transformers, etc) but the circuit is a starting point with your output transformers and power supply. I attached the schematic for you. Most people buy the Tubelabs PCB, but it will not fit your chassis, so point-to-point wiring is your option.
Is there a problem with your existing power supply and MIEC capacitors? If there is no problem I would not change the capacitors. If you must change the multi-caps look at: https://www.tubesandmore.com/products/capacitors?filters=746a130c112a746
Here is the Tubelab website with information on the SPP amp that I mentioned. https://tubelab.com/pc-boards/tubelab-spp/
EDIT: @FlaCharlie posted while I was typing. I agree with all he says.
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@ Francois G, thanks for the info. Since there is a PC board and the project is a beginning level, I may be able to build that. It would be just for training, though. My Pilot is a rather nice, clean sounding amp w/ 15W/channel. I had thought about duplicating that design with improvements like multiple OHM taps on the output transformers and level controls. If I put 2 of those together, I'd have the ideal for my odd set-up. However, I was having trbl matching the power transformer from Hammond and just dropping in their output transformers likely wouldn't work unless I had enough knowledge to do some tweaking (because feedback circuits are probably fussy, among other things). Since I'm happy listening to what I have, I'm prb not doing anything near term beyond continuing to study. Thanks to everybody for all the advice.