I am sick of failing amplifiers

Kingrex

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Feb 4, 2019
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I'll restate as previously: I bought those amps as the original owner directly from Audion, then in the UK. I made no changes to them myself other than tubes. About four years in, one of the solid state rectifiers blew. I took both amps to Bob Hovland and asked him to replace and upgrade the rectifiers in both amps so they would be the same. I also asked Bob to inspect the amps for any other problems worth correcting and to make suggestions for improvements he thought worthwhile making.

Bob replaced and upgraded the rectifiers in both amps. He suggested recapping the power supply to get faster charge/discharge than the stock caps, which would improve dynamics, definition and bass. I agreed. He also said he could make the amps quieter by fabricating a custom shield for the power transformers, going so far as to precisely position them by ear and by meter. Last, he rerouted some of the signal wiring for lower noise and made some grounding improvements. He did not want to make signal component changes as that would likely change the voicing of the amps. I also agreed. No trouble ever after that. Before I sold them to Kingrex, I took them back to Bob for inspection and asked him to replace suspect components. They got a clean bill of health and when both amps left Los Angeles, there were no (as in zero, none) mismatched parts in those amps. They worked perfectly, and by the way, Bob's noise abatement resulted in the amps testing -10db from as they tested before the changes, and -12db from Audion spec.

Now, Kingrex knows I have a long string of text messages from him after he got the amps, outlining that HE was inside the amps making changes on the fly, which I advised him not to do. He also texted to say at one point that after I coached him through an initial rough start that the amps were quieter than his push-pull amps and sounded "way better." Sometime after that some kind of trouble started and the amps got shuffled in succession to -- by my count followed here -- at least three other techs I know nothing about. Geeze Louise, he even ragged on the importers tech.

It's like every time you change dentists the new guy claims he would have done everything better than the last dentist and the one before that. But every time he claims any of these problems originated with me or Bob Hovland, he is deflecting, blatantly misrepresenting. Those amps left Los Angeles with no problems and all parts matched between them, included the many tubes I sent him above and beyond the deal. If anyone here has seen Bob Hovland's work, you'd know that what Kingrex is describing didn't originate in Southern California. Good luck with Electr-Print xformers. I just sold a couple of amps for a friend transformered with custom Electra-Print. Let's just say the Black Shadow pair I had were drum-tight in the bass region and lightning-quick by comparison. Audion's OTLs fall apart below 200 Hz? The amp is rated 24w. Well, I guess anyone can test them up to, say, 32w to see what happens.

Phil
I will admit, the tall thin caps Bob installed in the power supply were better than the stock ones the Audion tech used to replace them with when he rebuilt the power supply.


Maybe you sent these to Bob before sending them out, and though they were in fine working order. I guess it comes down to your acceptance level of noise and issues. Up to a week ago, no one has been able to connect any front end component to the amps without a very loud ground loop hum. Which your answer to my complaint about this was to send me a couple Ebtech HumX ground lift cheater plugs. That issue has finally been resolved since I found this new tech. I can ground the amps as they should be. Would you like them back?

I have our text string too as well as a lot of other email with other people telling me what they saw inside the amps. Phil, you have the gift of gab. I'm sure you could sell sand to a guy living in the desert. But I trust the performance specs my current technician supplied. These amps were modified from where you had them by the Audion Tech, so I don't know exactly all he may have done. Maybe Audion added back in distortion. But I think something else happened.


The changes I had done by Audion were replacing the volume potentiometer with the Audion stepped ladder resistive attenuator.

I had the signal coupling cap changed to a VCap

I had the power supply rebuilt

I had the ceramic signal tube sockets changed to a German brand I do not know the name that is suppose to have excellent dampening qualities.

I had the 845 tube socket changed to one made from billet aluminum.

The flimsy tin plate the signal tubes mount to is now supported by Aerospace isolators used to protect circuit boards on space ships.

I really don't see how what I had done would have affected the bandwidth of a transformer. I thought that had more to do with the materials and manufacture process of the transformer itself. Maybe you weren't playing anything below 200 hertz. That can easily be done by adjusting the coupling caps. I found that out during my trials of getting the bias set right for the Elrod, ACME and Linlai tubes. There is a parallel cap around the bias resistor that limits the bass response of the amp. You had a 22 uf cap in there. The current schematic has a 47 uf.

Maybe you like distortions in your music. Maybe Bob knocked it down from where it came from the factory. I am not sure how changing the caps in the power supply would make that go to .5% at less than a watt. Maybe you couldn’t hear the deficiencies in the output transformer with all the noise. You were also running the tubes at very high dissipation rates. They redpated every tube I put to them accept for the psvane hifi and 1 shuguang. I think the shuguang C took the power. The bias was outputting at least 100 watts. You did tell me I was going to redplate some of the Shuguang you gave me, but the bias resistor could be adjusted to fix that.
The changes I had done probably revealed a lot of noise you were living with but didn’t realize was there. From this point on the amps were running stable but tubes were red plating and I was hearing the distortion issues that were most likely buried by the low quality stock components provided in the base model amps you purchased.



Locally I had the bias resistor changed and I had the 22 uf capacitor in that circuit changed to a 47uf. The cap change did lower the bass and I heard more slop and less control.



Last week I had the front end rebuilt. That got rid of the grunge (.5% distortion) I was able to hear when the better components were added to the amp. And it rid the amp of the ground loop. Thank god. I abhor nothing more than amps with floating grounds. It’s just wrong to cheat a ground. It serves other purpose besides safety.

I would love to have the Monolith Magnetics transformers. They don't fit. Electraprint do. I am using what is available. Once the new transformer are in, these amps should actually play to a very high level.
It has been a long road. I don’t suggest others take it. I would be very hesitant to ever purchase a 20 year old amp again. But I actually think these amps are going to work very well with my PAP Trio 15 horn so I am excited to reach the end of this road. 2 weeks from now and hopefully the rebuilds will be done.

If you say you did your due diligence before sending these to me, then fine. I accept you acted in good faith. But that makes me think you really didn’t know what you were using. You must not have realized all the problems that plagued these amps. But hey, we have debates all the time on these forums how our ears actually like the distorted noise tube amps make. It can be pleasing. Maybe your listening taste differ from mine. I like tubes. But I like them to be quiet and extended in frequency response. I spend my working days shedding noise from electrical infrastructure. So maybe I am sensitive to it.

Rex
 

thedudeabides

Well-Known Member
Jan 16, 2011
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Alto, NM
Sounds like a long slog. Are you a happy camper yet?
 

Kingrex

Well-Known Member
Feb 4, 2019
660
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Sounds like a long slog. Are you a happy camper yet?
Kind of a deep question. While much of this journey and the one that preceded it with the Ampsandsound Casablanca were stressful. Along the way I learned a lot. I much better understand the dynamics at play between amps and speakers. What to listen for. What is a positive change and what is just different. They are two very different things.
I also understand better the dynamic interaction between your house power and your audio equipment. If I had no been fighting issues with equipment, I blamed on my electrical infrastructure, I may not have pursued modifications to my electrical power supply as vigorously as I did. All that focus and effort lead me to a new business model. So yes, I am a very happy camper. Estatic.

In a very singular perspective of do I like my amp and they way they interact with my speakers. Well, I have a little more ground to cover. I can hear the smear and lack of control the output transformer presents. Now that the front end is much more clean and revealing, the bass is more resolved and you hear where it breaks up and falls apart. If I can drop the bandwidth down to say 40 hertz to 45 hertz and have it stay in control, then as a whole, the amps will be in a much better place.
And then there is the bias. I get why Audion and Phil are driving the tubes to their maximum dissipation levels. They are more dynamic and staccato. They play with more snap. But I'm going to burn through $1500 a pair tubes. I was told their is a fuse in the circuit to protect the amp when the power tube blows. That is a bonus.
And when it came back from the Audion tech, it had more calm and balance, but I do believe the capacitors Bob had used in the power supply added snap and punch. My current tech said the power supply is very stiff. It performs very well. That is one of the best attributes of the amp. Under dynamic strain it provides continues even power. So I don't really know I want to screw with that any more.

The amps are getting there.
 

213Cobra

Well-Known Member
Aug 27, 2018
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Los Angeles, CA
I will admit, the tall thin caps Bob installed in the power supply were better than the stock ones the Audion tech used to replace them with when he rebuilt the power supply.


Maybe you sent these to Bob before sending them out, and though they were in fine working order. I guess it comes down to your acceptance level of noise and issues. Up to a week ago, no one has been able to connect any front end component to the amps without a very loud ground loop hum. Which your answer to my complaint about this was to send me a couple Ebtech HumX ground lift cheater plugs. That issue has finally been resolved since I found this new tech. I can ground the amps as they should be. Would you like them back?

I have our text string too as well as a lot of other email with other people telling me what they saw inside the amps. Phil, you have the gift of gab. I'm sure you could sell sand to a guy living in the desert. But I trust the performance specs my current technician supplied. These amps were modified from where you had them by the Audion Tech, so I don't know exactly all he may have done. Maybe Audion added back in distortion. But I think something else happened.


The changes I had done by Audion were replacing the volume potentiometer with the Audion stepped ladder resistive attenuator.

I had the signal coupling cap changed to a VCap

I had the power supply rebuilt

I had the ceramic signal tube sockets changed to a German brand I do not know the name that is suppose to have excellent dampening qualities.

I had the 845 tube socket changed to one made from billet aluminum.

The flimsy tin plate the signal tubes mount to is now supported by Aerospace isolators used to protect circuit boards on space ships.

I really don't see how what I had done would have affected the bandwidth of a transformer. I thought that had more to do with the materials and manufacture process of the transformer itself. Maybe you weren't playing anything below 200 hertz. That can easily be done by adjusting the coupling caps. I found that out during my trials of getting the bias set right for the Elrod, ACME and Linlai tubes. There is a parallel cap around the bias resistor that limits the bass response of the amp. You had a 22 uf cap in there. The current schematic has a 47 uf.

Maybe you like distortions in your music. Maybe Bob knocked it down from where it came from the factory. I am not sure how changing the caps in the power supply would make that go to .5% at less than a watt. Maybe you couldn’t hear the deficiencies in the output transformer with all the noise. You were also running the tubes at very high dissipation rates. They redpated every tube I put to them accept for the psvane hifi and 1 shuguang. I think the shuguang C took the power. The bias was outputting at least 100 watts. You did tell me I was going to redplate some of the Shuguang you gave me, but the bias resistor could be adjusted to fix that.
The changes I had done probably revealed a lot of noise you were living with but didn’t realize was there. From this point on the amps were running stable but tubes were red plating and I was hearing the distortion issues that were most likely buried by the low quality stock components provided in the base model amps you purchased.



Locally I had the bias resistor changed and I had the 22 uf capacitor in that circuit changed to a 47uf. The cap change did lower the bass and I heard more slop and less control.



Last week I had the front end rebuilt. That got rid of the grunge (.5% distortion) I was able to hear when the better components were added to the amp. And it rid the amp of the ground loop. Thank god. I abhor nothing more than amps with floating grounds. It’s just wrong to cheat a ground. It serves other purpose besides safety.

I would love to have the Monolith Magnetics transformers. They don't fit. Electraprint do. I am using what is available. Once the new transformer are in, these amps should actually play to a very high level.
It has been a long road. I don’t suggest others take it. I would be very hesitant to ever purchase a 20 year old amp again. But I actually think these amps are going to work very well with my PAP Trio 15 horn so I am excited to reach the end of this road. 2 weeks from now and hopefully the rebuilds will be done.

If you say you did your due diligence before sending these to me, then fine. I accept you acted in good faith. But that makes me think you really didn’t know what you were using. You must not have realized all the problems that plagued these amps. But hey, we have debates all the time on these forums how our ears actually like the distorted noise tube amps make. It can be pleasing. Maybe your listening taste differ from mine. I like tubes. But I like them to be quiet and extended in frequency response. I spend my working days shedding noise from electrical infrastructure. So maybe I am sensitive to it.

Rex
In fact, as I said, the amps were -12db from spec wrt to noise after Hovland's mods. -10db from where they were before his mods. They were quieter than some push-pull tube amps I've heard in my systems and quieter than most any other SET I've tried or others brought through here. When the amps left LA there were no unmatched parts. The amps were set to run 100w dissipation tubes from the factory, which the Chinese graphite tubes, like the 845A, 845B can handle, per the RCA spec. The only tube I sent you for alternate-sonic purposes that I warned would redplate was the Shuguang 845C metal plate, a 70w dissipation tube with 20% less output. It doesn't go runaway but if you llke its sound, I advised the amp should be rebiased for it. No other tubes I sent you ever redplated for me. But my systems are on autoregulators, fed steady 119.9-120v. If you have higher voltage incoming, then it could run differently. I regulate my systems' voltage because I get 122 - 128 from LADWP.

Audion specs distortion at 0.1% or less, at 1w. They do not offer a distortion rating at full power. I had my amps measured multiple times while I owned them, including in the final check before shipping them to you. They measured better than spec. However, no one can legitimately represent a zero-feedback SET amp as distortionless. At full power you might see 2% - 5% THD in those designs. You seek immediacy and transient speed, along with tone density from Audion SET, not five decimal-places THD.

We discussed bass characteristics in a phone conversation. I explained that on Zu Druid 6, where the Greiwe-cab FRD rolls off below 29-30Hz, the first signs of bass bloat called for correcting via narrowing the floor-to-plinth gap, which cleaned it up nicely. On Zu Definition 4, the sub driver handles bass below 38Hz in my setup, but the Black Shadow did not drive the sub driver. In the Zu Def, the sub Class D amp derives its input signal from the full range amp output, so while essential sound characteristics of the main amp are present, the driver is controlled by the output and damping of the Class D amp in the sub section. As a result, the rising distortion deep bass characteristics are nicely mitigated. In that conversation I said given your sound priorities as expressed to me, I thought you'd probably biamp but you should try the amps full range to get to know them.

When you first contacted me, I ticked through a range of amps I could make available to you and initially I discouraged you from considering the Black Shadows and suggested better push-pull tube amps than the ones you were struggling with. You came back saying, "...no, I really want to try SET.." Well, if so, the drive and energy you were looking for made the Black Shadow a good vehicle to determine whether you'd like SET. However, if you try to make what is now a $14K/pr SET amp sound like some combination of a push-pull pentode and solid state amp, you will never stop spending money on it. Remember, if you buy a retail $13,995 pair of monoblocks, to have a distribution channel that maker has to have no more than ~$2800 in materials, parts & labor, total, in the *pair* of monoblocks. So, $1400 each in total cost, in order to support multi-tier distribution.

I knew and know what to expect from that cost level, when making a conscious decision to choose SET. If they were $60,000/pair, and sold through distribution, they would have to have no more than $12,000 in total production costs. If you want to turn your Black Shadows into $60,000 retail SET amps, that's your call. It seems you have embarked on a campaign to try. My point is that none of the problems you've described originated with me or Bob. I limited my upgrades because, as Bob noted, changing out everything that could be changed out will leave you with something else, which you can't predict.

Phil
 
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RogerD

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May 23, 2010
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At this point in my life I decided to buy only one brand of vintage preamps and amplifiers even though by a lot of audiophiles they have a signature sound. Why because it is by far the only brand that has factory authorized service centers that work on used older gear of their make. Those service centers guarantee their work and they specialize in that brand. I no longer want problems.
I use Audio Classics in New York and so far I'm happy and I can supply parts....what's not to like.
 
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Atmasphere

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May 4, 2010
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My current tech said the power supply is very stiff. It performs very well.
Wait- we're talking about an SET, right? By definition they are class A; unless operating A2 or A3 (the latter patented by Jack Elliano of Electra-Print) the draw on the power supply is constant. So yes it would be 'very stiff'; whatever that means when the current draw is invariant... nearly regardless of the filter capacitors installed.
 
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Kingrex

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Feb 4, 2019
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The new output transformers I had installed were a knock it out of the park success. Absolutely transformed these amp. Holly cow I am in love with these amps now. I have it all. Bass where I can hear low organ notes. Speed where a stand up is alive and real. Clarity that exposes interplay of musicians as I have never heard in my system. Decay so vivid I heard a closing note in a song I never heard before. And I have played this song hundress of times and ask people to play it on their systems.

I am shocked. I never realized the output transformer had that much influence on the overall of the amp. I have heard people say it. But when you hear one transformer come out, and another replace it with such a profound impact, it drives the claim home. The transformer I got was a single tap 6 ohm. I'm glad I took Jack of Electra-prints advice. He said he likes the single taps better than the duel 4/8 ohm.

Unless something really catastrophic happens, I don't see trying any other amps. These really could be my end all amp.

The guy who did all the work, Rene, he says he can make them even better. He does not like the layout of the circuit board for the power supply. And he says the caps could be improved upon. Maybe after these are well broken in I will let him take it a little further. But they are so darn good now, it makes me nervous I could mess it up. But hey, he designed and installed a new input stage, dumped massive amounts of noise and made them sing. So I trust he knows what he is doing.

So, another failed amp has come to life, better than ever. Thank goodness there are a few good tech left in the world. I was thinking Ralph with Atmasphere was one of the only left. It appers there are at least two.
 
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Kingrex

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Wait- we're talking about an SET, right? By definition they are class A; unless operating A2 or A3 (the latter patented by Jack Elliano of Electra-Print) the draw on the power supply is constant. So yes it would be 'very stiff'; whatever that means when the current draw is invariant... nearly regardless of the filter capacitors installed.
I think what he was saying was as the current i creased the voltage stayed stable in the circuit.
 

Atmasphere

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I think what he was saying was as the current i creased the voltage stayed stable in the circuit.
That requires regulation. Otherwise if you increase the current, the power supply output will sag. It will sag at a slower rate with more capacitance. But with a class A1 circuit (which is about 98% of all SETs) the current is constant at all power levels.
 

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