X-202: How to Maximize Sound Quality?

[ssouci]

I have a Fisher X-202 integrated amp

wondering what other owners are are doing to squeeze the most out of their amps in terms of SOUND QUALITY, and to a lesser degree, reliability

what things have you done that provided the greatest and most worthwhile improvements in sound quality, in terms of time and dollars invested?

some improvements are easy, cheap, and make a noticeable difference... while others (especially if difficult or complicated) might not really be worth the effort... would be great to be able to prioritize

I suppose there are three broad categories:

1. HARDWARE RESTORATION
- bringing the unit back to good working original condition... mostly replacing worn parts, but also cleaning and adjustments

2. HARDWARE MODS
- alterations to the original design, mostly wiring or parts changes

3. REPLACEABLES
- mainly the vacuum tubes, but possibly also ancillaries like input attenuators, cables, etc.

personally, I've gone through a basic restoration with my X-202 (mostly caps), made a few mods (guided largely by info on AK), and currently I'm thinking about the tubes... EG: exactly which tube brands and models are best, and which tube positions matter the most and should receive the most attention for an X-202 specifically... I'll try to post a summary soon

anyone else out there with an X-202?

would love to exchange info here if possible

PS: I'm referring to a plain model X-202 (aka The Executive), not an X-202-B

thank you!

 

[RS Steve]

The X202 is one of my favorite Fisher tube amps, being a combination of their SA-100 amp and 400-C preamp. I have restored (3) of them over the years and feel they are great sounding pieces. I found that doing a usual complete restoration gets them sounding excellent once again. This includes capacitor replacement, replacing the major resistors with better rated and tighter spec pieces, installing strong quality known tubes, and doing the mod that allows you to easily test, and adjust the bias without going inside. Installing EFB would be the upgrade that brings this unit to the best it can be, a mod I have yet to take on and master.

 

[ssouci]

here's a summary of what I've done so far...

RESTORATION
1. replaced all e-caps (electrolytic caps), including the red tubular German e-caps (all of these were bad)... replaced all with 105C rated parts, plus "long-life" versions when possible
2. replaced all large filter caps with custom-made "multi-value" units, and/or adding individual caps underneath
3. replaced all mylar film caps on volume control etc. (at least one was going intermittent)
4. replaced all resistors in the output tube area with new metal film type (for greater reliability and stability)
5. replaced all indicator lamp bulbs with new
6. cleaned all controls and tube sockets
7. replaced damaged (cracked bare wire) wiring to tube heaters
8. visually checked all solder joints and wiring
9. set Phase Inverter adjustment electrically (using multimeter)
24. replaced all coupling caps with new films or Russian PIO

MODS
10. increased capacitance value of all large filter caps
11. installed 4 SEPARATE bias measuring resistors and connected them to 4 EXTERNAL test points to permit easy individual bias setting... test points now located at the unused terminals available on the speaker terminal strip (resulting from removal of the speaker damping circuits)... no more opening up the case to check/set the bias!... set bias to exactly 29 mvdc on each tube, very stable
12. removed/modified the original low frequency limiting circuit including installing different film caps... allows the very lowest frequencies to pass through now
13. eliminated remote control option... removed all wiring associated with that socket, "dummy plug" no longer required
14. added 2 bypass film caps to reduce noise (as per "The Fisher Doc")
15. installed "screen stability" resistors on the output tubes... used metal films
16. defeated "Phase Reverse" slider switch and eliminated signal path going through contacts... right-channel speaker now connected directly to output transformer… speaker terminal connections were altered accordingly
17. defeated "Low Filter" slider switch and eliminated signal path going through contacts (shorted signal path right at the terminal strip, instead of at end of long connection leads)
18. defeated "High Filter" slider switch and eliminated signal path going through contacts (relocated wires on the switch)
19. defeated "Tape Monitor" slider switch and eliminated signal path going through contacts (relocated wires on the switch)
20. rearranged order of jewel indicator lamps to be symmetrical (orange-red-orange) during normal stereo operation... made more sense to me, plus I didn't like having too many colours and just didn't like the green colour... not original I know, sorry!
21. install a CL-80 inrush current limiter
25. switched the 4 rubber chassis feet to taller ones (approx. 1" high)

REPLACEABLES
22. output tubes: installed quad of NOS vintage Russian 6P14P-ER tubes (10,000 hour rated military)... these are known 7189 equivalents... they sound great to me, BUT, I have no idea if a set of "real" 7189 tubes (eg. Mullard) would be any better (???)
23. pre-amp tubes: installed high-end 12AT7 tubes in positions V3, V4 & V5… eg. Telefunken ECC801S… still waiting for one tube to arrive, so not sure how all this will pan out, and if I will notice any improvement in SQ (???)

 

[larryderouin]

You have a link or a source for #14??? We've found over the years that mods by "The Fisher Doc" are mostly either ineffective, or detrimental to SQ and operability of the amp/preamp/tuner/receiver.

 

[ssouci]

You have a link or a source for #14??? We've found over the years that mods by "The Fisher Doc" are mostly either ineffective, or detrimental to SQ and operability of the amp/preamp/tuner/receiver.

RE: "14. added 2 bypass film caps to reduce noise (as per "The Fisher Doc")..."

I believe this is his suggested mod:
- add 0.01uF/630V cap from junction of R82 and C43B to ground
- add 0.01uF/630V cap from junction of R86 and C46A to ground

(those are Fisher ID codes)

I have no idea if this is a good, bad, or useless mod (I don't have the technical knowledge to determine that), but imagine he certainly must have his reasons for recommending it... I just followed instructions... my amp did not blow up anyway!

LOL... I've noticed a few references online about the Fisher Doc, they seem to be either positive or negative... I sure don't know all the history with him, but have to say that I was in direct contact with him a while back, and he was overall very good to me, he did help me out, and I am thankful... although, he did (very clearly) state that the previous owner of my X-202 had pretty well destroyed it, and that I should just sell it or use for parts, and to find a new unit to start over with!... not what I had wanted to hear, but he was quite right in some respects

no way I wanted to start over, so I plugged away with my unit and tried to clean it up as best I could (the wiring of the large filter caps in particular was messy and scrambled, and it took a while to get back to the stock config, which I eventually accomplished)...

also, I don't think it's all that easy to even FIND another X-202... I've always wondered: how many X-202s did they make, when (and what year was mine manufactured?), and how many still survive today...

Q: does anyone know?

he's definitely a "real character" from what I can tell... regardless of anything else, it is great that he's helping to keep old Fishers alive

 

[ssouci]

here's my COOLING setup

made of 3 computer fans (80mm "quiet" ones) epoxied to a piece of wood, in turn mounted to an old Dell computer monitor stand (very stable)... powered by an old wall outlet power supply (old phone charger???), with output that gives slower/quieter fan running speed

this is a standalone cooler, NOT connected in any way to the X-202... could be used with other amps

I barely notice it running, and I can run my amp for hours on end, and the main power transformer only gets "fairly hot" -- instead of broiling hot!... the output transformers remain cold, and the rest seems fine... of course tubes will be hot still... this setup helps to heat the room in winter no doubt

also, I plug the amp power cord into a basic count-down timer ($15)... I have to push the button each time to send power to the amp, then it runs for 6 hours, then shuts down... very handy since I never have to worry about accidentally leaving a tube amp running unattended for excessive hours or days!

 

[ssouci]

added to my list, under MODS: "switched the rubber chassis feet to taller ones (approx. 1" high)"

I believe that this will definitely help in cases of natural convection cooling, especially if the amp is sitting on top of another warm component... even when using a cooling fan like I do, it should help somewhat, and sure can't hurt

the taller rubber feet I added are solid, but pretty chintzy-looking and poorly made (super cheap, from China)

they're OK for now, but I'm still looking for a source of better ones, preferably some with some vibration isolation capability... seen some fancy ones, but they're too expensive

 

[walyfd]

Simply put--stop once you feel happy.

Personally, I'd much rather have an original, untouched modified amp that Avery himself may have heard and approved from the factory line...

 

[ssouci]

Simply put--stop once you feel happy.

Personally, I'd much rather have an original, untouched modified amp that Avery himself may have heard and approved from the factory line...

of course, I can TOTALLY understand that, and an "all original" unit has it's benefits and is what many people like

however, I decided right off the bat that my unit was not going to be one of those... when I bought it, it already had some changes that were irreversible, and was partially "restored", so the decision had already been made for me... so I've had nothing to lose by making any of the changes I have, because it simply can never be an original unit again... it's quite liberating!

so, I've just been doing things that firstly put it into good, reliable (and safer) working order... then, some that perhaps can improve upon the sound quality, which is very important to me

it's interesting also to consider that, when this amp was made, the music sources and quality of recordings were nowhere near what they are today, and I'll bet Avery would have done something quite different if he was designing and building the same amp in the year 2020... and if he had available to him components with the specs, capabilities, and (low) cost of what is available today... I'm able to incorporate some of those, making the unit better in some ways

it's surprising just how capable this amp (and other similar vintage tube units) are at sound reproduction, even when compared against the latest & greatest modern amps... in many cases, it beats them!... and in the process, is definitely much cooler to own and to look at a vintage tube amp... and the beat up faceplate gives it even more character, imho

I think it's pretty neat to connect two wildly different eras together... IE: feeding a modern digital source (CDs in my case), into something using the oldest possible technology... somehow (and incredibly) the two can actually be connected electrically, work together, and sound great!.... I might even get a music streamer one of these days, making the contrast even greater

all I know is that I love this amp, and its sounds great to my ears... has a lot more soul than any solid state unit I've ever owned (not that I've owned hundreds or anything, but enough to know I guess)... sure, it could use a bit more power for when I want to *really* crank it, but realistically, that doesn't happen too often... I usually listen at above-average levels though ("proper" level), and it's totally adequate for that, even though my speakers are not super efficient

 

[Linehand]

here's my COOLING setup

made of 3 computer fans (80mm "quiet" ones) epoxied to a piece of wood, in turn mounted to an old computer monitor stand... powered by an old cheapo power supply (old phone charger???), with output that gives slower/quieter fan running speed

I barely notice it, and I can run my amp for hours on end, and the main power transformer only gets "fairly hot" -- instead of broiling hot!... the output transformers remain cold, and the rest seems fine... of course tubes will be hot still... this setup helps to heat the room in winter no doubt

also, I plug the amp power cord into a basic count-down timer ($15)... I have to push the button each time to send power to the amp, then it runs for 6 hours, then shuts down... very handy since I never have to worry about accidentally leaving a tube amp running unattended for excessive hours or days!

I setup fans above output tubes and main xfmr- as long as they were running everything was ok. I had rearranged and forgot to switch them on for about 5 min before I could smell plastic burning. I changed them to drawing air behind tubes and xfmr and works well on or off. Cool amp you got there.

 

[ssouci]

RE: #22 above (output tubes)

actually, I did try a quad of vintage USA-made Tungsol 7189 tubes... there were clearly not as good as the Russian 6P14P-ERs (that I already had in), so they went to a new home

the Russians sound better overall, and noticeably more beefy and powerful somehow

...still dying to know what other (actual) 7189 tubes would sound like in my X-202... it's obviously very difficult to do that, since I can't go around buying up quads of 7189s just to try! (not easy to find them, and expensive if you do)

 

[larryderouin]

Theory behind the bypass caps on the mains is allowing more high frequency stuff to go thru which the main cap won't or can't do due to size of the cap. I've seen it done (either factory or mods) on Solid state stuff where the bandwidth is great enough to allow an increase in high's. Unless you scope it and can do a sweep up to at least 25kHz and it shows a flatter hi freq with little or no drop off (<2db), I don't think you'll notice the difference in SQ for the highs.

Done mainly on Receivers or amps with Main Filter caps of 6800uf and larger where it's more prevalent and the bypass caps are usually sized to be about 1/1000th of the Main. With the Size of the Mains on the X-202 (C43 is 1Kuf and C46 is 40uf) I seriously doubt there is or will be much if any change noted.

 

[ssouci]

has anyone used in-line ATTENUATORS with an X-202?

did they help improve the sound and/or reduce the sensitivity of the volume control?

(I've made post on AK regarding the subject of using attentuators in general... click here)

thanks!