Hi All,
Looking for some insite into a possible latent failure mode in a pair of amps I am restoring...a sanity check on my reasoning etc...
The GFA1 amp is spec'ed as a stereo, 200w/8ohms, 350w/4, it has a big toroid, fan cooled heatsinks, 10A fuses on primary side, ergo approx. 1kw consumption. Not unreasonable for a high output, high curent amp...even as parts they would be worth the $110 I paid for the pair...but...
The amp as originally designed is bridged, and I don't mean that it's a monoable amp, I mean each of the 2 channels is comprised of a pair of 50-60w amps that are bridged. Nothing intrinsically wrong with that, passlabs, jeff rowland etc make some great bridged amps.
The issue is that each of the 50w amps has a single 2sd424/2sb554 (150w/15a) pair for the outputs, which again as a 50w amp would be fine. But if my understanding of transistor ratings and SOA curves is correct this output stage doesnt have seem likely to have a long and healthy life driving full power into 4 ohms.
The output rails seem to be approx. +/-50v so the absolute max output voltage swing (assuming 10% regulation on PSU, transistor losses etc) will be approx. +/-80v. This already implies peak currents in excess of the transistors ratings, and if one considers the peak power rating of the output transistors they seem to be well past the point of destruction...or am I missing something...I planned on using these as sub amps, but I don't want to spend time, effort and money fixing the amps only to fry them if someone gets enthusastic with the volume...I'd rather take care of the issue, upgrade 'em now while they are in pieces all over the table.
Assuming this analysis is OK, anyone know of more substantial TO3 outputs, of course they need to be similar to the toshiba's characteristics to...
Thanks for any help
Stuart
Looking for some insite into a possible latent failure mode in a pair of amps I am restoring...a sanity check on my reasoning etc...
The GFA1 amp is spec'ed as a stereo, 200w/8ohms, 350w/4, it has a big toroid, fan cooled heatsinks, 10A fuses on primary side, ergo approx. 1kw consumption. Not unreasonable for a high output, high curent amp...even as parts they would be worth the $110 I paid for the pair...but...
The amp as originally designed is bridged, and I don't mean that it's a monoable amp, I mean each of the 2 channels is comprised of a pair of 50-60w amps that are bridged. Nothing intrinsically wrong with that, passlabs, jeff rowland etc make some great bridged amps.
The issue is that each of the 50w amps has a single 2sd424/2sb554 (150w/15a) pair for the outputs, which again as a 50w amp would be fine. But if my understanding of transistor ratings and SOA curves is correct this output stage doesnt have seem likely to have a long and healthy life driving full power into 4 ohms.
The output rails seem to be approx. +/-50v so the absolute max output voltage swing (assuming 10% regulation on PSU, transistor losses etc) will be approx. +/-80v. This already implies peak currents in excess of the transistors ratings, and if one considers the peak power rating of the output transistors they seem to be well past the point of destruction...or am I missing something...I planned on using these as sub amps, but I don't want to spend time, effort and money fixing the amps only to fry them if someone gets enthusastic with the volume...I'd rather take care of the issue, upgrade 'em now while they are in pieces all over the table.
Assuming this analysis is OK, anyone know of more substantial TO3 outputs, of course they need to be similar to the toshiba's characteristics to...
Thanks for any help
Stuart
I assume they are TO-3P (plastic) and not TO-3 metal. The GFA's
I used to own had the TO-3P outputs. If by chance they are metal
I would change them to MJ15024's and 25's. If they are P's I have had good luck with 2SA 1302's and 2SC3281's
Personally I have driven these amps on a 4 ohm load and ended up with smoke. It is my opinion that a better designed amp be used for the task. I share the same feeling for the Crown designs that also contain two 60 watt amps in bridge mode per side.
Joe
I used to own had the TO-3P outputs. If by chance they are metal
I would change them to MJ15024's and 25's. If they are P's I have had good luck with 2SA 1302's and 2SC3281's
Personally I have driven these amps on a 4 ohm load and ended up with smoke. It is my opinion that a better designed amp be used for the task. I share the same feeling for the Crown designs that also contain two 60 watt amps in bridge mode per side.
Joe
output trannies...
Thanks for your reply.
These are 'real' TO3 metal cases, based on my web searchesnot many people are aware of these particular Adcom amps, as far as I know these are their first products and precede all the multi digit GFA amps by some years.
The schematic was drawn in 1979...updated in 1981, apparently for the GFA1a, which has different protection circuitry, probably needed to defend the output stage...
I'll look into the motorola transistors, the different package doesn't bother me too much, in fact in the plastic form I may be able to use more transistors, paralleling them...
Stuart
Thanks for your reply.
These are 'real' TO3 metal cases, based on my web searchesnot many people are aware of these particular Adcom amps, as far as I know these are their first products and precede all the multi digit GFA amps by some years.
The schematic was drawn in 1979...updated in 1981, apparently for the GFA1a, which has different protection circuitry, probably needed to defend the output stage...
I'll look into the motorola transistors, the different package doesn't bother me too much, in fact in the plastic form I may be able to use more transistors, paralleling them...
Stuart
i had one years ago. it used to3 metal can output devices. in my opinion, this amp was built before adcom made the step up to the robust designs of the later products. in general, my opinion is one should not used a bridged design to drive 4 ohm loads unless it was specifically designed to do so.
mlloyd1
mlloyd1
Greetings,
I am also in the process of repairing a smoked GFA-1. One side burned driving 6 ohm speakers. Inside I found the drivers on the good side had previously been replaced with 2SB600 and 2SD555. Since they survived, I'm going to replace the burned 2SD424 and 2SB554 outputs with them. They are available in matched sets from ampslab.com.
I've been looking for the schematic for the GFA-1, where did you find yours?
Gord
I am also in the process of repairing a smoked GFA-1. One side burned driving 6 ohm speakers. Inside I found the drivers on the good side had previously been replaced with 2SB600 and 2SD555. Since they survived, I'm going to replace the burned 2SD424 and 2SB554 outputs with them. They are available in matched sets from ampslab.com.
I've been looking for the schematic for the GFA-1, where did you find yours?
Gord
schematic
Hi,
Thats an easy one, Adcom. They have been very generous, I've asked them several times for service manuals and they have always eiher emailed them to me or sent them snail mail. The GFA1 came on paper or I'd just pass it on.
I used mje15030/31 drivers and mj15003/4 output pairs, having fixed it I tested the amp into 4 ohms (resistive) to maximum power with no problems.
Stuart
Hi,
Thats an easy one, Adcom. They have been very generous, I've asked them several times for service manuals and they have always eiher emailed them to me or sent them snail mail. The GFA1 came on paper or I'd just pass it on.
I used mje15030/31 drivers and mj15003/4 output pairs, having fixed it I tested the amp into 4 ohms (resistive) to maximum power with no problems.
Stuart
Re: schematic
THe Mj15003/4 would be close to the perfect upgrade for 554/424 used in lower rail designs. The other choice would be the Mj21195/96's which are manufactured under TOS licensed processed tht created the 424/554/600/555 in the first place.
Stuart Easson said:
THe Mj15003/4 would be close to the perfect upgrade for 554/424 used in lower rail designs. The other choice would be the Mj21195/96's which are manufactured under TOS licensed processed tht created the 424/554/600/555 in the first place.
Hey Stuart,
You got those on Ebay didn't you! I didn't know much about 'em but I was actively bidding. You beat me at the end of the auction.... Thank You🙂 ...really!
Marc
You got those on Ebay didn't you! I didn't know much about 'em but I was actively bidding. You beat me at the end of the auction.... Thank You🙂 ...really!
Marc
I know this is a super old thread.... But I am too thinking about using one of these as a sub amp. I have a Dayton DVC310-88 12" Subwoofer in a small sealed enclosure and planned on using this amplifier as the amp.
After hearing about the issues in this thread, I'm having second thoughts. The voice coils are supposedly 8ohm each and 4 ohm if ran in parallel. Any thoughts guys?
First post - thanks for your help!
After hearing about the issues in this thread, I'm having second thoughts. The voice coils are supposedly 8ohm each and 4 ohm if ran in parallel. Any thoughts guys?
First post - thanks for your help!
Actually thats easy.
Fortunately the GFA1 can drive 8 ohms quite well, you have two amplifier channels and two voicecoils, so use one channel for each 8 ohm voice coil...
Voila, 400w into 4ohms.
The amp is actually quite a lot more powerful in the short term, having approx. 50v rails.
Since each channel is already internally bridged, I'd leave them completely separate on the output side and simply use a 'Y' on the input.
HTH
Stuart
Fortunately the GFA1 can drive 8 ohms quite well, you have two amplifier channels and two voicecoils, so use one channel for each 8 ohm voice coil...
Voila, 400w into 4ohms.
The amp is actually quite a lot more powerful in the short term, having approx. 50v rails.
Since each channel is already internally bridged, I'd leave them completely separate on the output side and simply use a 'Y' on the input.
HTH
Stuart
I would have to give you a big no on using a dual voice coil subwoofer with this amplifier and the concept of dual voice coil drivers where stereo program will be used. Dual voice coil drivers in general.
First of all the impedance will certainly dip below 8 ohms at low frequencies with this driver. Secondly it is a very bad idea to use it in conjunction with a dual voice coil driver because the program may have differences which will make one channel try to correct these differences thru the feedback loop which will cause a stability problem and sooner or later the destruction of the amplifier.
I have fought this concept in commercial systems where poor planning had resulted in the usage of dual voice coil drivers in certain instances and sooner or later resulted with fried amplifiers.
You do what you want however. Just for the record I owned two of these amplifiers when they first came out. I thought I had the answers also and tried this very same approach driving a dual voice coil subwoofer off this amplifier. The result was the distruction of the amplifier. Luckily I was still under warranty and was lucky enough to receive a new amplifier out of the deal.
My answer is based on actual experience and not just a "I think it will be ok"
First of all the impedance will certainly dip below 8 ohms at low frequencies with this driver. Secondly it is a very bad idea to use it in conjunction with a dual voice coil driver because the program may have differences which will make one channel try to correct these differences thru the feedback loop which will cause a stability problem and sooner or later the destruction of the amplifier.
I have fought this concept in commercial systems where poor planning had resulted in the usage of dual voice coil drivers in certain instances and sooner or later resulted with fried amplifiers.
You do what you want however. Just for the record I owned two of these amplifiers when they first came out. I thought I had the answers also and tried this very same approach driving a dual voice coil subwoofer off this amplifier. The result was the distruction of the amplifier. Luckily I was still under warranty and was lucky enough to receive a new amplifier out of the deal.
My answer is based on actual experience and not just a "I think it will be ok"
Very good points...
...but if you read closely you will see I did not recommend using the amp and woofer with stereo signals, hence the "Y" on the inputs, and no connection between channels at all on the outputs.
Basically used as I described the amps are independently driving each voice-coil with (to the accuracy of the resistors setting the gain on each channel) identical signals. There is no way for one channel to "try and correct" anything in the other, and the amp will not be any more or less stable than it would have been driving any other 8ohm speaker.
As to the voice-coils having a dangerous impedance at low frequencies that could be an issue and the quick answer would probably be to measure (or look in datasheet) the impedance of the woofer concerned at DC, (the lowest possible) and if needed (Rvc < 6ohms) replace the output transistors. With 8 transistors to replace this 'problem' can be fixed quite inexpensively. Luckily the transistors are in sockets, and IIRC there is no bias adjustment, so it is pretty straightforward.
Basically if one accepts this amp can drive an otherwise unexceptional 8ohm load, then each channel can drive an 8 ohm voice-coil. After all it is just as if it were connected to any other 8ohm speaker, at low freq the woofer in a full range system does not have any form of impedance correction.
As you have seen if you drive 4 ohm loads hard or connect the output of one channel to the other it is pretty much guaranteed the magic smoke will come out.
HTH
Stuart
...but if you read closely you will see I did not recommend using the amp and woofer with stereo signals, hence the "Y" on the inputs, and no connection between channels at all on the outputs.
Basically used as I described the amps are independently driving each voice-coil with (to the accuracy of the resistors setting the gain on each channel) identical signals. There is no way for one channel to "try and correct" anything in the other, and the amp will not be any more or less stable than it would have been driving any other 8ohm speaker.
As to the voice-coils having a dangerous impedance at low frequencies that could be an issue and the quick answer would probably be to measure (or look in datasheet) the impedance of the woofer concerned at DC, (the lowest possible) and if needed (Rvc < 6ohms) replace the output transistors. With 8 transistors to replace this 'problem' can be fixed quite inexpensively. Luckily the transistors are in sockets, and IIRC there is no bias adjustment, so it is pretty straightforward.
Basically if one accepts this amp can drive an otherwise unexceptional 8ohm load, then each channel can drive an 8 ohm voice-coil. After all it is just as if it were connected to any other 8ohm speaker, at low freq the woofer in a full range system does not have any form of impedance correction.
As you have seen if you drive 4 ohm loads hard or connect the output of one channel to the other it is pretty much guaranteed the magic smoke will come out.
HTH
Stuart
Actually I will stand on my comment to not use this amplifier with a dual voice coil driver. Because its bridged and because the impedance of this driver and many like it WILL dip in impedance at lower frequencies. I have the impedance meters and have done many many test of 100's of different drivers by different manufacturers. Any difference between the two sides of that driver WILL result in problems. They are best used as either in a
parallel situation or a series situation. We know the amplifier will not tolerate a situation where the voice coils are paralled. It would be best to sell that amplifier and purchase one capable of driving a parallel voice coil load of 4 ohms and use one channel of the amplifier to drive that load.
parallel situation or a series situation. We know the amplifier will not tolerate a situation where the voice coils are paralled. It would be best to sell that amplifier and purchase one capable of driving a parallel voice coil load of 4 ohms and use one channel of the amplifier to drive that load.
adcom gfa-1 one hell of an amp
it is my biased opinion that the gfa-1 has plenty of power and is robust. but just like a high performance race motor if you screw up everything will blow apart.
first i am not a "pro" in as i do not understand the complex circuity of this amp i believe there are many more transistors than you are seeing at first glance and they share the load.
second there are many many ways you can do things wrong and only a couple ways to do it right.
do not use or run this amp. on anything other than 8 ohm (my biased opinion)
i used and recommend a set of altec 604 duplex studio monitors 16 inch. i used a bi-amp then got tired of the extra wires and equipment and had a custom set of crossovers built. then built a custom set of cabinets call altec they will send you a set of recommended. cases they didnt make cabinets back when i was using them b/c they are built to be mounted in the wall at the studio. my cases are double thick 3/4inch plywood approx. 2.5x2.5x3 foot and with the element weigh around 100-120lbs each.
unless you are deaf more sound then you will ever need in a home setting.
in college i hosted parties and ran this system at 3/4 vol. for 6 hours straight about 150 times over a 5 year period
again my biased opinion 80% of the time the adcom gfa-1 gets damaged its because you other equipment could not handle it and when that equipment fails it takes the amp with it..
unless you use high power high quality speakers the speakers will blow when pushed. and you wont even see or hear it coming b/c the amps power is so clean and robust the speakers will sound amazing until they self destruct.
same goes for anything else wires, pre-amp etc etc.
again my totally biased opinion this gfa-1 is way more powerful than rated,
i mean this dam thing actually makes an impact on you electric bill if pushed long and hard.
the GFA-1 will burn up and fixing them is expensive and time consuming pia
i know this b/c we got drunk and bored and when ever someone had a set of speakers they wanted blown up i obliged. several times we have guys bragging about how assume their speakers were and i would tell them, i dont care what you think about your speakers i bet you a hundred bucks this GFA-1 will blow them apart before 3/4 volume.
and many were dumb enough to take that bet. 7 of the 8 sets i blew up never made much past 50%. a set of JBL made it to 3/4 then blew apart so violent that the woofer coil landed 15 feet on the other side of the room. i would say 5 of the sets didnt last 2 min.
but set number 8 when they blew it took the amp with it.
now i know i could run the altecs at 3/4 for hours so it was the speakers that took down the amp. (i know nothing scientific with this b.s.) and many audiophiles are now upset they spent 2 mins reading this crap.
point being the power with the GFA-1 is so clean and extreme you need to use very high power high quality components and self restraint.
i would say the output on the GFA-1 is north of 300 watts.
also note i never abused or mis-used my equipment again after spending 3 months and paying $250.00 to get it fixed (1990s dollars). it was really difficult finding some one to fix this.
just one reason is if you mis anything or have one leaky transistor it will re-fry the amp. and all the transistors you just replaced.
use 8 ohm and dont use any sub-standard components or something or everything will get cooked.
on chat pages like this guys have fried thousands of dollars worth of equipment. and you can lose everything amp, pre-amp, speakers and anything in between.
i believe there is a video some where of a guy arc wielding with a GFA-1 amp.
in fact its so powerful i rarely use it any more, 90% of my listening is with and old 70 watt Yamaha. the Yamaha is a pre-amp or integrated amp can switch back and forth so now and then i use as a pre-amp and fire up the GFA-1 but the fan alone is noisy and not a good amp for easy listening.
point #29 lol back in the day i had an extra fan hooked up behind the GFA and if you like it loud i recommend the extra fan b/c it gets pretty hot
so use GFA- 1 and altec 604 duplex and go loud or go with a different amp choice. and setup i would say for 99 out of 100 audiophiles the gfa is not a good choice . but for that one guy that wants to shake the glass out of the windows, go for it.
it is my biased opinion that the gfa-1 has plenty of power and is robust. but just like a high performance race motor if you screw up everything will blow apart.
first i am not a "pro" in as i do not understand the complex circuity of this amp i believe there are many more transistors than you are seeing at first glance and they share the load.
second there are many many ways you can do things wrong and only a couple ways to do it right.
do not use or run this amp. on anything other than 8 ohm (my biased opinion)
i used and recommend a set of altec 604 duplex studio monitors 16 inch. i used a bi-amp then got tired of the extra wires and equipment and had a custom set of crossovers built. then built a custom set of cabinets call altec they will send you a set of recommended. cases they didnt make cabinets back when i was using them b/c they are built to be mounted in the wall at the studio. my cases are double thick 3/4inch plywood approx. 2.5x2.5x3 foot and with the element weigh around 100-120lbs each.
unless you are deaf more sound then you will ever need in a home setting.
in college i hosted parties and ran this system at 3/4 vol. for 6 hours straight about 150 times over a 5 year period
again my biased opinion 80% of the time the adcom gfa-1 gets damaged its because you other equipment could not handle it and when that equipment fails it takes the amp with it..
unless you use high power high quality speakers the speakers will blow when pushed. and you wont even see or hear it coming b/c the amps power is so clean and robust the speakers will sound amazing until they self destruct.
same goes for anything else wires, pre-amp etc etc.
again my totally biased opinion this gfa-1 is way more powerful than rated,
i mean this dam thing actually makes an impact on you electric bill if pushed long and hard.
the GFA-1 will burn up and fixing them is expensive and time consuming pia
i know this b/c we got drunk and bored and when ever someone had a set of speakers they wanted blown up i obliged. several times we have guys bragging about how assume their speakers were and i would tell them, i dont care what you think about your speakers i bet you a hundred bucks this GFA-1 will blow them apart before 3/4 volume.
and many were dumb enough to take that bet. 7 of the 8 sets i blew up never made much past 50%. a set of JBL made it to 3/4 then blew apart so violent that the woofer coil landed 15 feet on the other side of the room. i would say 5 of the sets didnt last 2 min.
but set number 8 when they blew it took the amp with it.
now i know i could run the altecs at 3/4 for hours so it was the speakers that took down the amp. (i know nothing scientific with this b.s.) and many audiophiles are now upset they spent 2 mins reading this crap.
point being the power with the GFA-1 is so clean and extreme you need to use very high power high quality components and self restraint.
i would say the output on the GFA-1 is north of 300 watts.
also note i never abused or mis-used my equipment again after spending 3 months and paying $250.00 to get it fixed (1990s dollars). it was really difficult finding some one to fix this.
just one reason is if you mis anything or have one leaky transistor it will re-fry the amp. and all the transistors you just replaced.
use 8 ohm and dont use any sub-standard components or something or everything will get cooked.
on chat pages like this guys have fried thousands of dollars worth of equipment. and you can lose everything amp, pre-amp, speakers and anything in between.
i believe there is a video some where of a guy arc wielding with a GFA-1 amp.
in fact its so powerful i rarely use it any more, 90% of my listening is with and old 70 watt Yamaha. the Yamaha is a pre-amp or integrated amp can switch back and forth so now and then i use as a pre-amp and fire up the GFA-1 but the fan alone is noisy and not a good amp for easy listening.
point #29 lol back in the day i had an extra fan hooked up behind the GFA and if you like it loud i recommend the extra fan b/c it gets pretty hot
so use GFA- 1 and altec 604 duplex and go loud or go with a different amp choice. and setup i would say for 99 out of 100 audiophiles the gfa is not a good choice . but for that one guy that wants to shake the glass out of the windows, go for it.
http://www.onsemi.com/pub_link/Collateral/MJ11012-D.PDF
With a bit of change these should work, under $3 at Newark.
Also, mount a big bridge rectifier to the tunnel and run wires down to the diode holes (remove the diodes).
With a bit of change these should work, under $3 at Newark.
Also, mount a big bridge rectifier to the tunnel and run wires down to the diode holes (remove the diodes).
Last edited:
Hi djk,
I have never had a bridge fail on these amps, and as a warranty shop for Adcom we saw many of that product line. These little fellas did output the power as advertised.
The 2SD600 pair mentioned above is an iffy sub. Thank goodness they are hard to find these days. That pair is rated at 200W and only 10 A. The 2SD424 / 2SB554 had a 150 W power rating and 15 A current rating. I generally used MJ15022 and MJ15023 for outputs back then. Never had one come back.
One thing that most people did not replace, but should have were the dual transistors in the complimentary diff pairs. These would be out of balance, so you simply match a quad (2 NPN + 2 PNP) and install those. The amplifiers would then be at least as good as new. We also changed the smaller capacitors at this time, the main filter capacitors were generally just fine. Done right these were nice little amplifiers.
Fan noise. Replace the fan if it is noisy. It's old enough to warrant a replacement, unless the fan is on high speed because you were pounding it. Sticking the amp way up high sometimes did the trick if you don't like any fan noise.
-Chris
I have never had a bridge fail on these amps, and as a warranty shop for Adcom we saw many of that product line. These little fellas did output the power as advertised.
The 2SD600 pair mentioned above is an iffy sub. Thank goodness they are hard to find these days. That pair is rated at 200W and only 10 A. The 2SD424 / 2SB554 had a 150 W power rating and 15 A current rating. I generally used MJ15022 and MJ15023 for outputs back then. Never had one come back.
One thing that most people did not replace, but should have were the dual transistors in the complimentary diff pairs. These would be out of balance, so you simply match a quad (2 NPN + 2 PNP) and install those. The amplifiers would then be at least as good as new. We also changed the smaller capacitors at this time, the main filter capacitors were generally just fine. Done right these were nice little amplifiers.
Fan noise. Replace the fan if it is noisy. It's old enough to warrant a replacement, unless the fan is on high speed because you were pounding it. Sticking the amp way up high sometimes did the trick if you don't like any fan noise.
-Chris
"I have never had a bridge fail on these amps, and as a warranty shop for Adcom we saw many of that product line."
I saw the diodes unsoldering themselves and falling out of the board!
Once that happed it was time for the 25A bridge.
I've got a 1 and a 1A laying around that need service.
I saw the diodes unsoldering themselves and falling out of the board!
Once that happed it was time for the 25A bridge.
I've got a 1 and a 1A laying around that need service.
Hi djk,
I guess we just don't run them that hard up here. I don't doubt that you have seen this.
A 25 A bridge is good medicine for failing rectifiers, no doubt!
-Chris
I guess we just don't run them that hard up here. I don't doubt that you have seen this.
A 25 A bridge is good medicine for failing rectifiers, no doubt!
I can't imagine a more capable person to sort them out than you. Just give up and take them completely apart, clean the heat sinks and transistors and replace the dead stuff, then reassemble. Heat sinks are good in the dish washer as long as the lady isn't anywhere about. Get the grease first though! It's just work, nothing to strain the mind.
-Chris
more gfa-1 posts
it is nice to see some interest in this old amp. i thought i was in a very small minority still using this amp. i should also note the amp. was completely rebuilt before i bought it. this might explain it performing better than expected. i do not know what the original owner did to the amp. just that he was one of the service tech. at hollowood music in pgh. and was selling it b/c b/c of the fan. he said he rarely used the amp at high volume and didnt like the fan at low volume. lol now i am the old guy that rarely turns his amp. up.
the other thing you might consider is the amp. is a bit bright or harsh with most pre-amps. i tried several and the only one i liked was the Yamaha i still have.
the yamaha is old and a bit of a hybrid it was made when they were moving from tubes to transistors. so it has a very nice sound,(to my ears).
the more i talk about this amp the more i realize it is not a practical amp. for most listeners. also note i did not do any of the technical work on the amp, it was done for me. I was told that this amp. is difficult to work on and setup "correct" so if one is doing their own work might want to consider this.
maybe things are different now but i had 6-10 people refuse to fix this amp for me. i had to track down the original owner (who) had changed jobs and have him fix it.
it is nice to see some interest in this old amp. i thought i was in a very small minority still using this amp. i should also note the amp. was completely rebuilt before i bought it. this might explain it performing better than expected. i do not know what the original owner did to the amp. just that he was one of the service tech. at hollowood music in pgh. and was selling it b/c b/c of the fan. he said he rarely used the amp at high volume and didnt like the fan at low volume. lol now i am the old guy that rarely turns his amp. up.
the other thing you might consider is the amp. is a bit bright or harsh with most pre-amps. i tried several and the only one i liked was the Yamaha i still have.
the yamaha is old and a bit of a hybrid it was made when they were moving from tubes to transistors. so it has a very nice sound,(to my ears).
the more i talk about this amp the more i realize it is not a practical amp. for most listeners. also note i did not do any of the technical work on the amp, it was done for me. I was told that this amp. is difficult to work on and setup "correct" so if one is doing their own work might want to consider this.
maybe things are different now but i had 6-10 people refuse to fix this amp for me. i had to track down the original owner (who) had changed jobs and have him fix it.
- Status
- Not open for further replies.