dowto1000
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The Psvane tubes worked in your amp because the signal level is higher, going into an amp, from the output of a preamp, than is the signal level inside a preamp. Got that !!
Dowto1000
Any Fi X3 300B amp owners out there?
- Thread starter grantray
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- 300b don garber fi audio
The Psvane tubes worked in your amp because the signal level is higher, going into an amp, from the output of a preamp, than is the signal level inside a preamp. Got that !!
Dowto1000
Orest12
Member
Greetings, All--
Completed the recommended resistor mod yesterday; must thank Dowto1000 and Palustris for this great suggestion. Took a while because of the cramped working space between the X panels. First impression upon turn on: the amp hum is still there but maybe a bit quieter; no worries there, nature of the beast. The hum pot now actually reacting for the first time with a range from quite loud to much less hum; it never had any effect before the mod. Sonically I am very tempted to say that there is noticeable improvement; will keep everyone posted after some more hours of listening. As mentioned before, I've had this amp for many years and didn't use it much. It always seemed rather average in sound quality and dynamics, bested by several other amps so there was no reason to use it. However, after the passing of Don Garber last year, I gave it another serious try just for sentimental/historical reasons; several things have changed it dramatically: connecting it to a ss Mc preamp instead of my usual Cary tube; using the Psvane drivers; and now the Dowto1000/Palustis resistor mod. I was most pleased and delighted listening to the Don Garber Fi X 300b stereo power amp last evening; it may well be as good as its reputation.
A few silly things now: the paper inside as mentioned was an old kleenex tissue, not the hoped for schematic. All those "less is more" believers will be pleased to know that there isn't much inside the amp; actually it might have more outside transformers (eight) than inside parts.
Finally, must thank Grantray for starting this thread; wondering how you are doing with your new treasure? Please consider adding the resistors to the hum pot.
Completed the recommended resistor mod yesterday; must thank Dowto1000 and Palustris for this great suggestion. Took a while because of the cramped working space between the X panels. First impression upon turn on: the amp hum is still there but maybe a bit quieter; no worries there, nature of the beast. The hum pot now actually reacting for the first time with a range from quite loud to much less hum; it never had any effect before the mod. Sonically I am very tempted to say that there is noticeable improvement; will keep everyone posted after some more hours of listening. As mentioned before, I've had this amp for many years and didn't use it much. It always seemed rather average in sound quality and dynamics, bested by several other amps so there was no reason to use it. However, after the passing of Don Garber last year, I gave it another serious try just for sentimental/historical reasons; several things have changed it dramatically: connecting it to a ss Mc preamp instead of my usual Cary tube; using the Psvane drivers; and now the Dowto1000/Palustis resistor mod. I was most pleased and delighted listening to the Don Garber Fi X 300b stereo power amp last evening; it may well be as good as its reputation.
A few silly things now: the paper inside as mentioned was an old kleenex tissue, not the hoped for schematic. All those "less is more" believers will be pleased to know that there isn't much inside the amp; actually it might have more outside transformers (eight) than inside parts.
Finally, must thank Grantray for starting this thread; wondering how you are doing with your new treasure? Please consider adding the resistors to the hum pot.
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dowto1000
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Golly....I can't see any added resistors from each end terminal of that three terminal pot, to the pot's center terminal. Am I missing something, or am I the only one who can't see it ??
If they are not connected, your listening report could be termed a placebo effect. What gives here , please tell us . Thanks.
Dowto1000.
Orest12
Member
Resistors were installed. Photo tries to show the cramped working space as the panels will not separate too far
because of the wiring on the panels. My placebo effect is usually in reverse—some time back a friend tried to impress me with his new multi- thousand dollar interconnect. I didn’t want to hear any difference between that and my humble wire, so I didn’t.
By the way, hope you approve of my resistor choice.
because of the wiring on the panels. My placebo effect is usually in reverse—some time back a friend tried to impress me with his new multi- thousand dollar interconnect. I didn’t want to hear any difference between that and my humble wire, so I didn’t.
By the way, hope you approve of my resistor choice.
dowto1000
BANNED
Good, no wonder I couldn't see them !! YES, I LIKE Ohmite Rs generally speaking, very OK IMHO.
Cheers.
dowto1000
BANNED
Power XFR, Choke, Filament XFR ( L), Filament XFR ( R ) Output XFR ( L ) Output XFR ( R ). Six, minimum I can think of.
Maybe a separate XFR for Filament to rectifier tube ( 5 Volt ) and to Filament of the Driver tube ( 6.3 Volt ), could make eight.
Dowto1000
dowto1000
BANNED
Well, there are certain functions, electronic requirements, that need to be covered in a circuit. You need enough " iron" to cover them all well. One function missing will be no sound. Just like a wheel missing on your vehicle will be : no - move. It is fine to have separate " iron", and , on the cutting edge ( which Don's amps never were, IMHO ). Some will say totally separate XFRs, for each function sound slightly better. Its miniscule IMHO.
There are many other far more important places, typically designer-neglected, where one can improve performance. The Fi basic circuit, ( somewhat like a Loftin White of 1929, two-stage tube amp, directly coupled ) is absolutely my personal favorite amplifier design. I would not build anything else for my VOTTs!!
But my own DIY world allows me to do what I want, with absolutely NO business or potential customer- pleasing constraints. I love this design freedom, ' am always seeking to improve tube amplifier implementations..
Dowto1000
grantray
Member
Wow, I got distracted with dadlife and this thread took on a life of its own in the most amazing way! Dowto1000, my 2A3 amp was not built by the late great Isamu Asano. It is called the Asano 2A3, based on the Asano circuit, developed by Isamu Asano's son as a stereo amplifier, and built/sold by EIFL's Yoshi Wakabayashi, (who also has a bonkers audio museum dedicated to Western Electric). My apologies for the confusion. Koji-san sent me a full set of RCA tubes with the amp, but I was surprised that the JJ 2A3-40 really is better performing (at least to modern sensibilities) than the very nice, NIB 1954 grey-plate RCAs that came with the amplifier.
As for the Fi-X3 300B amp, I'm really excited by the resistor mod! And yes, I'd love to read your paper on the history DC SET
Orest12, how's the amp sounding now that you've had a little time with the resistors installed?
As for the Fi-X3 300B amp, I'm really excited by the resistor mod! And yes, I'd love to read your paper on the history DC SET
Orest12, how's the amp sounding now that you've had a little time with the resistors installed?
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dowto1000
BANNED
Wow, I got distracted with dadlife and this thread took on a life of its own in the most amazing way! Dowto1000, my 2A3 amp was not built by the late great Isamo Asano. It is called the Asano 2A3, based on the Asano circuit, developed by Isamu Asano's son as a stereo amplifier, and built/sold by EIFL's Yoshi Wakabayashi, (who also has a bonkers audio museum dedicated to Western Electric). My apologies for the confusion. Koji-san sent me a full set of RCA tubes with the amp, but I was surprised that the JJ 2A3-40 really is better performing (at least to modern sensibilities) than the very nice, NIB 1954 grey-plate RCAs that came with the amplifier.
As for the Fi-X3 300B amp, I'm really excited by the resistor mod! And yes, I'd love to read your paper on the history DC SET
Orest12, how's the amp sounding now that you've had a little time with the resistors installed?
You have PM, through Audiokarma, just sent.
Yes, for many good internal design reasons, the JJ 2A3-40 will easily outperform any and all 2A3 biplates, in a good amp, which has a supply and execution designed to get the most out of the JJ's unique construction.
Need your email address to send 32 page DC amp write up. Notice my AVATAR, a direct couple.
Dowto1000
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grantray
Member
Hi Jeff.
If the pot's center wiper and resistor is changed to a wiper-interface by the pair of soldered resistors, would the 25ohm resistor create a greater sweep than the 15om resistor?
If the pot's center wiper and resistor is changed to a wiper-interface by the pair of soldered resistors, would the 25ohm resistor create a greater sweep than the 15om resistor?
dowto1000
BANNED
Yes, a 25 Ohm resistor across the pot would have a slightly greater sweep. Its actually TWO 25 Ohm Rs across a pot, so 50 Ohms versus 30 Ohms, across whatever is the end-to-end resistance is of the pot.. Use Ohms Law - paralleled resistors, if you have to know.
We just want to get a SOLDERED path in place, not only just a wiper - to - resistive element interface - to offset the pot's subtle degrading diode effect, on the return-to-ground path of the Finals tube.
Isamu's DC 2A3 amp uses NO 2A3 filament pots, ( nor do my own 2A3 and Type 45 DHTs ever use a pot. ) Less is more.
Dowto1000
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Orest12
Member
Greetings Grantray and All, regarding the resistor mod, I am now convinced (at least 90%) that there is some sonic improvement—more drive, more dynamic. Also, as mentioned the hum pot now reacts from loud to the original hum; it never did anything before. Glad I did the mod; doesn’t look pretty because of the clumsy quarters, but the connections are secure. Thanks to the two members for the suggestions and it is recommended.
Two questions—what preamp are you using Grantray? Any thinkering with your x3, tubes, speakers, etc.?
Two questions—what preamp are you using Grantray? Any thinkering with your x3, tubes, speakers, etc.?
grantray
Member
Interesting. Is the hum level the same as before, with the difference being the sweep from loud hum to less so?
As for my X3, I've swapped the drivers to a pair of older used but good RCA 6sn7 tubes I had laying around, and I'm currently running direct to source while I rebuild the power supply in my McIntosh C20. (The parts are in, I just need to find the time.) I've come to the conclusion that my example was barely used, as it as greatly improved with regular play. The hum is still there as before, but I generally tune it out on all but the quietest pieces.
As for my X3, I've swapped the drivers to a pair of older used but good RCA 6sn7 tubes I had laying around, and I'm currently running direct to source while I rebuild the power supply in my McIntosh C20. (The parts are in, I just need to find the time.) I've come to the conclusion that my example was barely used, as it as greatly improved with regular play. The hum is still there as before, but I generally tune it out on all but the quietest pieces.
dowto1000
BANNED
Orest12 !!!!
Good for you !! You heard it !!
Your Fi amp SHOULD have more drive, because you have made the Finals tube, ( a " direct access to the music 2A3 tube" ) have a far better ( soldered, not a hum pot's purely mechanical - diode - like interface !! ) return path, for the tube's instantaneous peak cathode currents return to ground.
Thanks for posting this, so others, open-minded, hopefully may benefit. Palustris will like seeing this confirmation, I think, also.
Imagine a SE amp where every aspect of the design and execution was optimized .........for maximum drive and dynamics.
That, Orest12, is what I spend much of my waking time, thinking about, HOW to accomplish. Dynamics and drive starts with the power supply ( IMHO, IME ), with all chokes under 20 Ohms, and continues with superbly thought out below-deck wiring runs.
Dowto1000
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dowto1000
BANNED
You should have a mu of 100 tube in the Fi's front end, like Don Garber employed, and as does Shishido, Asano, Uthus and Fraker also employ. NOT a 6SN7 which " passes a signal " but only has a mu of 20 !!!
Maybe a good pair of 6SL7s, ( mu of 70, as a MINIMUM mu ) but no 6SN7. Too low of a gain, even if you have an active preamp before the amp, .....the amp's overall presentation of music suffers. ( IMHO, IME ).
Dowto1000
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Orest12
Member
Regarding the amp hum, the level might be slightly less after the resistor mod, but now the pot allows me to make it louder. Dowto1000, I am intrigued by your suggestion to try 6sl7 drivers. Garber shipped the X3 with 6sn7 tubes and I have many of these. Does the 6sl7 have the same current draw and operating voltage as the 6sn7 and can it be safely substituted for the latter? One of the many transformers on the X is probably for the filament. I have none of these tubes but could get a pair easily.
I also have not used this amp very much, only recently becoming interested in it after Don Garber’a passing.
I also have not used this amp very much, only recently becoming interested in it after Don Garber’a passing.