Fisher X-100 hurting my ears

pqrannes

pqrannes

Tubes warm your heart too
I've just bought a very nice looking Fisher X-100 (no dash A/B/2 or 3) - it is the one with the rectifier GZ34 tube.

The amp is in overall very fine condition and since it came with a quad of JJ El84s (and not 7189s) I ordered and got a quad of Sovtek el84Ms.

It is my plan you use the amp with my Danish three way Klipsch Bella'ish horns. And I am trying it out as I write this.

It does not sound bad, but it is a bit more clear/distinct at the top than I am use to with my other tube amps: the Braun CVS-13 (pp el84) amp, my Philips AG9015 (PP el86) amp and my little American Shell (SE El84M/7189) Northport.

The sound is not as 'fat' and tube-like as I know it from other tube amps.

Actually it wears my ears out.

After some listening I get very tired in my head and I almost have a ring in my ears. In a way it is very similar situation as when I first started to use my Braun on the three way horns: it rang in my ears until I found out a "presens" button that boosted the 1kHz to 15kHz by 6db was turned on! When I turned it off my problems were gone.

Well, back to the Fisher.
I gave the Fisher a try with another pair of speakers (Dynaco/Scandyna A-25 Xl) at a local vintage gathering this Saturday. We were listening to a vinyl record and I had to turn it off. It didn't sound right at all. It was much more bright than I have ever heard the A-25s even with SS gear (they are never bright, are they?).

I have tested all the tubes except the GZ34 on a very good (AVO 160) and newly calibrated tube tester. I've even put in vintage ECC83s that test better than the ones the Fisher came with.

The Fisher looks kind of unrepaired under the bottom with the plate off, but - note this - I know that the volume pot has been changed (the on/ff part didn't I was told from the seller).

The new pot seems to be a 1M ohm (it says so on it) but I am not sure that this is was the schematics suggest.

My question is thus this: can the wrong volume pot change the sound the way I describe it above?

I know the best to do is to recap the whole amp but it is not within my reach for the time being. I might get there one day but until then I just like to be able to listen to the Fisher without hurting my ears.

Peter Q (Denmark)
 
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Hi,
I have an X-100-3, as you can see from the picture on the left. I haven't used an X-100, and the X-100-3 does not use a tube rectifier. So, your experience may differ from mine, but I'll tell you what I've learned rolling 7189 output tubes in my application.
I had some 6BQ5s around and some 7189s around and I've tried a number of them. You can use a 6BQ5, but they won't last.
Here's what I've tried, what I use, and how I ended up there.
1. Amperex Bugle Boy 6BQ5 - bright and fatiguing - used.
2. Telefunken 7189 - bright and fatiguing - used.
3. New Mullard 7189 - Tested for 30 hours - bright and fatiguing. Bought new.
4. Sylvania 7189 - The sweet spot and my daily use output tube. I've now assembled a second quad just in case. I can listen to them all day without a problem.

Setup:
Thorens TD320 with AT 440ML OCC cartridge
Cambridge Audio Azur 840C
Fisher X-100-3 (see picture at top left)
Spendor SP1/5s. The European equivalent of these limited production run speaker would be 15/2. An LS3/5a type of mini-monitor.
Hsu STF-1 sub.

Now before you condemn your output tubes, try rolling some different 12AX7s in the input stages too. Best wishes and JJs are not known for their complementary characteristics in Fishers.
Don
Don
 
You have to recap it before making any sort of judgement. Not only are those old caps shot (as you know), but that technology has come a long way since the 50s. I beleive the edgy sound you are hearing is the direct result of crappy caps. Stick some nice orange drop 716Ps in there, and listen to it smooth out. Another fantastic cap if you want to spend a little more, is the Auricap brand. After that, the rule of thumb is Tele AX7s to brighten it up, Mullards to get that "lush" tube sound so many like, or Amperex to do everything right. Of course this is all just my opinions and YMMV. The thing is, that amplifier has great iron, and other than that, all thats left are the bits and pieces (mainly caps and tubes) to ruin the fidelity. Good luck with a great amp.:thmbsp:
 
I agree with jay- It is overdue for a recap. I think it will make a big improvement. Then from there you can try other tubes. John
 
Thx audiodon657, jaymanaa and sloober for your fast feedback.

I am aware that a recap is necessary in order to judge the full potential of the Fisher amp as a piece of hi-fi equipment. But I am not that far yet; I just want to able to listen to it. And I am not able to do that at the time being!

I am not very sensitive, not very high ended when it comes to hi-fi so it is not a matter of getting the best out of the X-100, but just getting it tolerable.

I being potential impolite I will return to the volume pot. As I read the schematics I linked to the original pot has a 500K tap while the substitute in my amp says "1 M Ohm" (I have the original pot but it has indication of the impedance); is that a problem for the sound or is the ohm rating of the pot decisive for how much (or little) you have to turn the pot to get a certain level of sound?

yours (with ringing ears)

Peter Q.
 
I'd like very much if some would comment on the volume pot issue: will a pot with different impedance than the original change the sound at all?

Peter (Denmark)
 
I'd try rolling some tubes first. That's the least intrusive way to see if you can mellow out the sound. I've no experience with substituting volume controls so I can't comment on that. I can't see why a pot of 2 times the potential of the original should be a problem though.
 
pqrannes said:
Thx audiodon657, jaymanaa and sloober for your fast feedback.

I am aware that a recap is necessary in order to judge the full potential of the Fisher amp as a piece of hi-fi equipment. But I am not that far yet; I just want to able to listen to it. And I am not able to do that at the time being!

I am not very sensitive, not very high ended when it comes to hi-fi so it is not a matter of getting the best out of the X-100, but just getting it tolerable.

I being potential impolite I will return to the volume pot. As I read the schematics I linked to the original pot has a 500K tap while the substitute in my amp says "1 M Ohm" (I have the original pot but it has indication of the impedance); is that a problem for the sound or is the ohm rating of the pot decisive for how much (or little) you have to turn the pot to get a certain level of sound?

yours (with ringing ears)

Peter Q.
Click to expand...

You say the pot has a 500k "tap". Does that mean it has more than 3 terminals per channel??
 
thx again for helping me out. I really appreciate this!

audiodon657: I'll do all the tube rolling I can, but for the time being I can only roll the ecc83/12AX7s. It is now fitted with Philips that I could substitute with Telefunkens. But to the best of my knowledge the TFs will only add more to top (if it is the treble that is the problem - I did some reading on "listener's fatigue" on the web, it might as well be the upper midrange that is bugging me!).

Besides the El84M that I can only roll with ordinary el84s (which don't take as much power) the phase splitters (7247s) could be rolled, but I don't have any.

jaymanaa: the old (and apparently original) volume pot that I now hold in my hand has three plus one taps on each channel. The mentioning of a 500K tap derives from the schematics I link to above; I'm not very skilled in reading schematics, you should know.

Peter (Denmark, thus the broken English)
 
OK, I see now. The original pot was a 500K with a tap at 125K. I don't think a 1meg. without said tap at 125K would work well at all, unless some other changes were made.:no:
 
The 125K tap is part of the "loudness" circuit. Look below the pot on the schematic and see the tap coming off the volume and going down into that circuit. If you don't have the tap, what is hooked that ???
 
Looks like he cut the value of C34 in half too. I would restore the unit back to stock instead of trying to figure out what the other guy was thinking.:no:
 
thx again,

I don't know if I confused you: The schematics I link to didn't come with the amp. I found it on the web. And yes going back with the the original pot must be the way. I was told that the on/off part of the pot didn't work but that is a minor thing.

The thing is the amp even hurts my ears with the loudness on! The is something weird going on somewhere in the middle!

And I'll take a closer look at the substitution pot and see how it is hooked up.

PQR
 
I'm sorry, I didn't read the previous posts very well. Yes, try to find an original volume control. There are a few things bad about having the wrong value and no tap. For one, the audio frequency tubes V2 and V7 should be looking at 500k there instead of 1meg. It just throws everything out of kilter. I'll check my stash of Fisher pots.
 
jaymanaa said:
I'm sorry, I didn't read the previous posts very well. Yes, try to find an original volume control. There are a few things bad about having the wrong value and no tap. For one, the audio frequency tubes V2 and V7 should be looking at 500k there instead of 1meg. It just throws everything out of kilter. I'll check my stash of Fisher pots.
Click to expand...

Turning the amp up side down with the bottom off shows there is an third tap but is it 125K?

I've been in contact with the guy who sold me the amp to me last week and according to him the tech that changed the pot is a skilled and trained technician with a good reputation.

Sorry to be such a novice but is there anyway I can measured the two pots (and compare them and their taps) with my multi-meter?

Peter
 
I agree with jaymanaa that putting this volume circuit back to original is probably a good idea. Fisher didn't throw anything together. Everything was well reasoned and presented the best output based on circuit compromises they made to achieve that quality output. I'm not saying that to disparage the quality of the work the tech did. He may be the best at what he does. But I'm a fan of upgraded but unmodified (for the most part) Fishers.
 
Can you take pictures of the unit under the chassis and post them to this thread? By the way, replacement on/off switches are available. Search on metalbone on the web. No, I'm not affiliated with him, but he sells a replacement switch, a thermister to act as an inrush current limiter, and detailed installation instructions as a package.
 
pqrannes said:
I am aware that a recap is necessary in order to judge the full potential of the Fisher amp as a piece of hi-fi equipment. But I am not that far yet; I just want to able to listen to it. And I am not able to do that at the time being!
Click to expand...

But honestly that's like saying "I know my car has a flat tire. But I just want to drive it anyway".

After 40 years I can pretty much guarantee the amp is not working anywhere near where it should be. And be very careful with that GZ34. If it's a good old stock piece it'll be destroyed if one of the power supply caps fails. :tears:
 
Thx,

audiodon657: I'll try to get a good picture of the volume pot under the chassis and post it.

Jim McShane: I understand you analogy.

But if I am - so to speak - on a flat tire now, sorting out the amps ringing in my ear issue (getting the volume pot right or understanding that new volume pot solution is not the problem) will fix the puncture and get me rolling: It might be on worn out tires but still rolling.

Totally recapping the amp is unfortunately out of my reach at the moment.

PQR
 
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