Paul and Bascom, could one or both of you comment on the sounds of the various coupling caps you evaluated? IIRC, both amps use Reliable’s AudioCap 'propylene-film-and-alum-foil caps; yes?
Boy, that’s a tough one. Probably the best description would be richness and fullness. The film and foil are just richer and fuller sounding with more detail and body than the metalized versions.
jeffreybehr saidIf memory serves me correctly, we didn't go through a lot of caps to decide what to use in the BHK amps and preamp. We had prior knowledge of the sonic qualities of the caps we did put in and they are indeed very good. However, Arnie Nudell and I tried quite a few different caps to bypass the caps in the amp. This yielded various degrees of improvement and the final choice was the Uptone Audio MusiCap 1uf/400V unit. Note we never took out the resident caps on the PC boards. The improvement with the MusiCaps added (4 in the amp) was quite profound. John Miller, who used to work with Arnie at Infinity on speaker design has replaced the resident caps in his BHK preamp and amp with very good results. A note on how I bypassed the resident caps. I soldered small clip leads to the end of the caps and just clipped them in over the leads of the resident caps.Paul and Bascom, could one or both of you comment on the sounds of the various coupling caps you evaluated? IIRC, both amps use Reliable’s AudioCap 'propylene-film-and-alum-foil caps; yes?
Thank you for your reply.
Just so I’m not confused–the caps in ‘a lot of caps’ are the couplers? And the caps in ‘bypass the caps’ are the powersupply caps?
Any idea what John Miller installed as PS caps (and bypasses) in his poweramps(s)?
Hi. we are talking about the coupling capacitors the 1 uF Rel Caps on both the amp and preamp circuit boards. John installed the Utone Audio MultiCaps either the 1 or 2 uF 400V units.
Here is an image of the caps in my amp
Paul McGowan saidBoy, that’s a tough one. Probably the best description would be richness and fullness. The film and foil are just richer and fuller sounding with more detail and body than the metalized versions.
Paul, TYVM for your quick reply.
Did you try any of the several Teflon-film caps?
No, we did not. As Bascom says once we landed on the 1uF types we liked it all had to do with the bypass. Do be careful of the caps you use and bypass with. There’s a lot of DC voltage potential difference those caps are blocking and any leakage is not good.
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Just to be sure I understand correctly–
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Original coupling caps are Reliable aluminum-foil-and-'propylene 1/400s;
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Bypassing them with Uptone MusiCap film-and-foil 1/400s or even 2/400s improves the sound. And a deduction there would be that the low-frequency filter point of these couplers seems not to be important; yes?
ANOTHER question/subject–are the main-PS caps bypassed? The decouplers (assuming there are decouplers)?
Sorry for the many questions–I’ve never had such good access to the builder and designer of poweramps I’ll be buying. 
Bump.
Just to be sure I understand correctly–
-
Original coupling caps are Reliable aluminum-foil-and-'propylene 1/400s;
-
Bypassing them with Uptone MusiCap film-and-foil 1/400s or even 2/400s improves the sound. And a deduction there would be that the low-frequency filter point of these couplers seems not to be important; yes?
ANOTHER question/subject–are the main-PS caps, which I assume are large 'lytics, bypassed? The decouplers (assuming there are decouplers)?
Sorry for the many questions–I’ve never had such good access to the builder and designer of poweramps I’ll be buying.
BHK here - The main power supply caps are bypassed with 0.1 uF film caps as are all the other supplies in the amps. There are no decouplers as such in the circuitry. The Low frequency corner of the tube to solid state coupling is 0.16 Hz ( 1uf & 1 Meg Ohm) and it is my firm belief that lowering this by another octave by paralleling another 1 uF is not what is affecting the sound - it is the result of the signal frequency qualities of the added capacitors. Not absolutely sure of the exact manufacturer’s details of the stock coupling capacitors. You could correspond with Rel Cap if you need more information.
Mr. King, TYVM.
- Reliable has COPPER-foil-and-'propylene-film versions of the original coupling caps; Sonic Craft has them.
http://www.soniccraft.com/product_info.php/pair-audiocap-pcu-1uf-400vdc-p-61
Rather expensive.
- I’ve finally ordered a pair of BHK 250s. I plan to try known-excellent-quality 1uF SoniCap Platinums (Teflon-alloy-film-and-tin-foil) and also (but NOT at the same time) the apparently-excellent Jupiter copper-foil-paper-and-wax caps in my amps.
Now you need to up your game with a DSD DAC!
…uhhh…might there be a six-channel version?
And about coupling caps, have you tried anything different in your '250? They appear to be easy to supplement. I THINK what I might try in mine is a 1uF Platinum and Jup. Copper in series, in parallel with the main caps, to get maybe 500 hours on the amps and these new caps, and then listen to them with only one installed in each of the eight positions. There ARE four per stereo amp, yes?
Others have suggested home theater versions of the DSD. It however appears impractical. Of course, you can buy three DSDs . . .
Un-HIJACKED My regrets
Will be eager to hear your opinions after burn-in. Also jeffrybehr’s after he installs and burns-in his.
Here I am more than two months after my '300s arrived, and I’m still not finished evaluating tubes. I guess that’s a logical result of NOT being a golden-eared audiofile(1) myself AND having had a total of 13 sets of tubes to break-in. The latter is finished, and I’ll start the quick-switch evaluations soon.
Still haven’t done anything with coupling caps; the little carton of Jupiter replacement/bypass caps is still sitting on my messy desk.
PAUL and BASCOM, could one or both of you comment on the choice of the very low (0.16Hz) filter point (FP) of the coupling caps? I’m more used to the three-octaves-below-20Hz rule-of-thumb which would have the FP at 2 - 3Hz. Any problem using a 0.1uF cap instead of the 1s(2)–in there?
(1) in the sense that I do NOT hear subtle differences quickly; I’m much more a a medium- and/or long-term listener.
(2) or higher if ‘bypass’ caps are added
It is really important to use low hinge points for frequency and that is why we have such large ones there. If we had our way we’d go even lower - not the other way.
I’ve made a little progress on my coupling-capacitor-replacement project for the BHK300s. I toyed with the idea of using Duelund’s relatively new CAST Cu/Sns, their hi-end PIO/wax/tinned-copper-foil versions, but at around $200 or $240 each for the 0.1s or 1uFs from Parts Connexion, I chose NOT to afford them. (Almost $2K for a set of coupling caps? YIKES!)
I’ve had a box of Jupiter Copper Foils for months but have simply not spent the time to finish evaluating tubes. Am about done with that and have been deliberating just how pricey to get with caps. After rejecting the above-mentioned Duelunds for their ridiculous prices (IMO, of course, and there are different, valid opinions about this sort of thing), I decided to take a lower-price approach and have ordered sets of the excellent-but-highly-affordable MultiCap RTXs(1) in both 1uF/200 and 0.1/200. I’ll install all three–0.1/600 Jupiters and both RTXs–in a maner that allows quick switching of any combination. (The original Rel 1/200 'propylene/tinfoils will be removed but could be clipped in later for comparisons.) With all three installed, I’ll be able to satisfy myself on the 0.1-v.-1uF issue and also on the Jupiter-v.-RTX quality question. I’ll post pics as I go along.
For more info–probably more than you’ll EVER want to read about capacitors–go to Tony Gee’s
http://www.humblehomemadehifi.com/Cap.html . Personally, within Tony’s evaluations and quality scale, I pay NO attention to caps with quality ratings lower than ‘10’. Also, more info on Duelund caps and other products is available at this pleasant, easy-to-read site…
http://jeffsplace.me/wordpress/ . Jeff LOVES Duelund stuff; maybe they are the world’s best.
HAPPY LISTENING, everyone. I’m sure loving the sounds of MY system.(2)
(1) The RTX uses tin foil and polystyrene film. All MultiCaps are multisection capacitors and are manufactured by Reliable Capacitor.
(2) …which is simply the BEST-sounding music-reproduction system I’ve ever heard…bar none…even tho it uses an A/V preamp. … 
… 
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I’ll be interested to read your eventual opinion of the Jupiter caps. I have these in my tube equipment and am very happy with the sound.