2. amps-preamps
  3. 1347227999

Please help with Spectron Musician Issue.

I haven't been on Audiogon in a while, but I now find myself at wit's end. I'd like to know if anyone can guess the problem, and where I might get it fixed... other than Spectron! (Read on.) I'm not very technical w/stereo equipment.

System: Spectron Musician II Class D amplifier, upgraded to the "Hybrid" version. Audio Horizons tube pre-amp. Resolution Opus 21 CD source. PS500 power conditioner. Magnapan 2.2R speakers. Good quality cables all 'round.

The short story:

The Left channel on my Spectron Musician II Hybrid amplifier drops out frequently. When it does, volume through the speaker goes way down, with an astounding amount of distortion. Just low-volume crackles and a disgusting trickle of music coming through. Sounds like a kazoo. In this condition, it's not likely to 'fix' itself. Other times, from startup, things sound great, but lately, it's been all bad.

I can often 'fix' the problem by disconnecting the right speaker cable (amp off, of course) so that I can hear the Left channel, starting the amp back up, and pushing the volume up quite high... almost to dangerous levels for the speaker. Most times, the channel will suddenly and sharply clear up -- I have to be ready on that volume knob! It's almost like pushing a clog through a drain. From there, the system might play fine for hours... or not. The left channel can drop out at any time, and lately, we haven't been able to get through a session without a problem.

I have eliminated ALL possible other components. Swapped speaker cables; went direct source to amp bypassing the pre-amp; tried different sources; tried RCA instead of XLR inputs. When the problem happens, it happens in the left channel of the amp despite any changes outside the amp.

Any ideas what the cause might be?

Now, here's where it gets really rich:

This amp has a history, and I know that by posting this note, I'll never be able to resell it. It has been back and forth to Spectron several times, perhaps four. One time, when John from Spectron was trying to debug an issue over the phone, he had me plug it in and fire it up, fire being the operative term. Something shorted out, smoke came up, little bit of flame. Quite spectacular.

It went out to California, and they pushed me to get an upgrade to the Hybrid version, well over $1,000 layout. I was pretty happy with the upgrade until just a few days after the warranty ran out, when the left channel issue came up.

Out to California again.Spectron said they'd honor the warranty. Spectron kept it for several weeks, and said they couldn't find any problems. Sounded normal to them, and they said they burned it for quite a while. (As I said earlier, it might play well for a while, and the problem is unpredictable.) They claim to have diddled one small, insignificant thing and sent it back.

Now they want to see the amp again (another couple of hundred in shipping costs), and yet their engineer can't even speculate what the issue might be. Clearly, I have little confidence that they'll fix the problem, and if I know Spectron, they'll try to cheap me out of more dollars. And yet, if I don't lay out more money, I have a boat anchor. Replacing the amp is not an option, financially speaking. Heck, Spectron makes the things, they should be able to repair them!

My questions:

Would you send the amp back to Spectron, given the circumstances?

If you did, would you have them honor the warranty on the upgrade, even though it has expired. I let them know about the issue BEFORE warranty expiration, but it cleared and I couldn't test it completely until AFTER warranty.

Do you have any idea what the problem might be?

Do you know of any wiz-kid repair person who does Class D work who would be a good alternative to a Spectron repair?

I've loved my amp... when it works. But this... this... is intolerable.

Thank you for your time and advice.

Rob Hanson
rhanson739
kijanki's avatar
kijanki
4,413 posts
 
Mcintech, It is not that difficult to fix it if you understand its operation. It is pretty much modulator chip + output Mosfets. If Mosfets are not driven then replace chip otherwise find bad Mosfet. I'm not sure why "it doesn't follow ohm's law" but if you don't like it then perhaps you don't use SACD (class D) or Sigma-Delta DACs (class D).
In spite of common believe, originated at noisy computer supplies, well designed switcher is quieter than linear supply and that's why Rowland uses them not only in the latest model 625 amp (class AB) but also in Capri preamp - where efficiency is secondary thing. Linear power supplies are also switchers of sort, that produce high frequency noise and 120Hz ripple difficult to remove. Rectifier diodes are switching at max voltage while good SMPS switches at zero voltage/ zero current. Linear supplies don't have line or load regulation (not to mention over-current protection) and require 10x larger power transformers and a lot of electrolytic caps to bring down 120Hz ripple. They are unprotected, unregulated, inefficient, noisy, large and clumsy - a Dinosaurs.
rhanson739 OP
269 posts
 
~
Mcintech -

Thanks for putting this into perspective for me.

You see, I never had any of the jobs you mentioned, nor do I have 32 years electronics repairs experience. Heck, I probably couldn't recite Ohms Law Theory on a bet. Clearly, then, I can't repair an amp of any type by myself. While your record is something you can be proud of -- and I'm sure you are -- it must also be a burden.

See?... I can own any darned amp I want to own, Class D, or otherwise. They're all the same to me, except for the sound quality.

:>)
kijanki's avatar
kijanki
4,413 posts
 
Rhanson739, I like your approach. I tend to over-analyze while at the end it comes to sound quality alone.
revrob
105 posts
 
I am curious to what the outcome is. I have the same problem recently. I thought it was my preamp, speaker cable, source and now I believe it is my Spectron Musician II that has been upgraded. My problem is the right channel plays great even for hours and then drops out so low you can barely hear it.

Please let me know what the outcome is as I will be contact Spectron next week.

Thanks
revrob
105 posts
 
Sorry, I meant the left channel same as your problem. It plays well and then the left channel goes completely out except for very faint music. Please keep me posted. I wonder if there are others with this same problem.

Thanks.
More to discover