[fz1jmp]

Hello all;
I recently picked up a beautiful AES (Cary) super amp with Svetlana 6550's, EH 6BQ5s and nos Amperex ECC88. I went from a pair of VR-3's speakers to Cornwalls just to complement the tube amp. I was running a pair of Pass Aleph 2's. Now, the Cornwalls sound great with the Pass's, rich deep and pretty smooth. When I flicked on the AES, wow was I disappointed! Listening to Cowboy Junkies Trinity revisited, the singers sound thin and light. With Mark Knopfler, veiled and just not clean and clear, almost distorted but not really.
So, any thoughts? I hate to have to sell the AES already, I was looking for a thick rich sound, I pretty much got the opposite. Think it could be the choice of tube? SHould I try some nicer KT88's?
Thanks in advance! (I put a pic just thought it may help)
Jack



I thought I would put my "final" thoughts. It turned out that the prior owner pulled his KT88's out, put in the 6550's and never re-biased, nor did he tell me to do it. I thought it was auto bias, but if you change out types of tubes, well you have to reset the bias. I actually went with some nos 6550's and they sounded great, after all that! However, I found a Hogan SET amp of my dreams and while I ended up enjoying the sound of the AES, especially with the Cornwalls, the AES is looking for a new home.

Thanks for all the great comments!!!!

[hibuckhobby]

I would try swapping the ECC88's and 6BQ5's first.
Your drivers often change the sound more than the outputs.
Hibuck....

[fz1jmp]

I would try swapping the ECC88's and 6BQ5's first.
Your drivers often change the sound more than the outputs.
Hibuck....

Thanks! I did not know that, I keep hearing so much discussion around KT88's and all the brands, I thought that was the bigger deal. I will start looking for an appropriate swap.

[Scott F.]

The Amperex (depending on the variant) should sound fairly decent. The EH 6bq5s are pretty hard and brittle sounding. I'd look at a pair of Telefunkens on eBay (less money than you would suspect) or even a pair of Mullards (not horribly priced either). I can't comment on the 6550s but the EH KT88s have a nice rounded sound (at least in my amps).

It shouldn't be too tough to smooth the sound out. Hang with it and do some tube swapping. That should cure your ills.

[fz1jmp]

The EH 6bq5s are pretty hard and brittle sounding.

Exactly what I heard, hard and brittle! I will hunt down some of your recommendations, thank you.

[rollo]

Agree the driver tubes do make a significant difference. If you desire rich try RCA.   Sletvana 6550s might help as well. I'm not surprised at all frankly. For years tubes ruled in my home. Started with Audio Research ended with custom Cyber 211SET mono blocks with NOS RCA 211s. Now hybrid class "D" mono blocks.
     BTW are the tubes in your Carey the original tubes ? Usually Carey's house sound is rich and a bit dark. If the carey sounds lean something is just not right. Was it modified at all ? Output caps ?


charles
   
   

[Early B.]

Are the amp and tubes broken in yet? Has the amp been sitting unused for a long time? Are all of the tubes functioning optimally?

[Quiet Earth]

I don't think tube rolling is going to change the inherent character of that amp. I would sell it and move on.

[rjbond3rd]

An amp's output impedance will affect bass output (so may be beyond tube rolling).

Consider doing one or some of the very simple, well-documented crossover mods to lower the output of the midrange squawker and tweeter relative to the woofer.  Generally speaking, this restores the speaker's bass balance.  The Klipsch forum is a great place for this.

[fz1jmp]

So, some more details. I'm running a Cary SLP-50B preamp with philips tubes. The amp was in very light use as a 2nd system. I see no issues with the amp itself and don't think, from what I can see of course, any additional issues. So, I have a Jolida 102 that I need to get repaired, but remembered I had some soviet 6BQ5's, which I tried and that make a audible difference, it somewhat softened the harshness, but did not seem to add to the detail. I listened for about an hour and while it sounded better, I'm sorry to say, to myself that is, that I like my Aleph 2's. It's one of those things where I want to like the AES better. My only reason to change in the 1st place, well besides my neurotic need to keep looking for a particular sound, I realized that the sound I'm looking for is my uncles 60's setup of Cornwalls and what I think was a Mc, but all my relatives are gone and I just don't remember. Now, I know some folks don't like that Cornwall sound, but they went a long way towards the sound I'm looking for. I thought the AES would bring me 'that' sound. Mc's have been somewhat out of my reach, but maybe thats where I need to go.

Anyway, thanks for the words. So, do tubes impart that much of a sonic touch where I should try a few different ones? I see a nice pair of tele's for around $90 from a good vendor. Or am I chasing my tail?

[Ericus Rex]

I seem to remember a Stereophile review of an AES piece back in the 90s that was not so flattering.  I don't remember if it was this amp though.

Tubes can make a big difference but tube rolling can be very expensive.  I personally, have never thought the 6550 was very good for audio.  The KT88 is much better suited for hifi IMO.  But, as Quiet Earth said, if the amp itself is not so great no amount of rolling will give you what you're looking for.

Are you sure the impedances match between amp and speaker?  If your amp has multiple output taps try a different tap and see if that improves things.

[Quiet Earth]

Just to clarify what I meant by my negative comment :  if the amp you bought is far from the sound you are looking for, it is probably better to just move on and get one you like. I didn't mean to imply that there is anything wrong with the AES amp, just that it is probably not what you hoped it would be. I have never heard that amp myself, but I know that tube rolling will only change the sound so much.

[munosmario]

Agree the driver tubes do make a significant difference. If you desire rich try RCA.   Sletvana 6550s might help as well. I'm not surprised at all frankly. For years tubes ruled in my home. Started with Audio Research ended with custom Cyber 211SET mono blocks with NOS RCA 211s. Now hybrid class "D" mono blocks.
     BTW are the tubes in your Carey the original tubes ? Usually Carey's house sound is rich and a bit dark. If the carey sounds lean something is just not right. Was it modified at all ? Output caps ?


charles
   
 

I totally agree with Charles. This particular amp represented Dennis Had's best effort to offer the Cary Audio Design "house-sound" to more frugal audiophiles (as a kit or assembled). Got rave reviews from many quarters and none of those reviews ever described the Super Amp sound as anything but at the level of pure CAD tube amp lineage (Google "Sounstage" review to see an example). The original power tubes were Chinese KT-88's which did more than just a decent job...tube rolling to KT-90" just added icing to the cake (tighter bass response).

So, the likely explanation to the OP's problem, aside of a misfortunate mix of rolled tubes (NOS or otherwise), as Charles suggests, could be a malfunctioning component or a modification (also misfortunate--or incompatible with the tube mix).

Mario

[fz1jmp]

Well, I'm going to say it 1 more time, thank you all so much for the education and words, all of the comments not only give me a different angle to think about, but teach me something and for that I'm indebted.

Now, some of my thoughts and clarifications; the amp is actually a bit of a 'special' amp, although a AES ae25 none the less. It's number 8 and as such had the following; Initially the units came with 6CG7 voltage tubes,dual triodes wired in parallel. This unit uses 6BQ5s in place of them. Also, in place of poly pro caps in most of the units now made this unit utilizes audio 1 paper in oil caps for all of the coupling and bypass caps. Newer units come with all electrolytic caps in the power supply. This unit has but 1 large input electrolytic cap and all the rest of the power supply caps are Solen large value poly caps supposedly making for a  much more responsive power supply when quick demands are needed. It's wired in pentode mode as opposed to triode mode also, I'm not sure if that matters.

I quoted most of the text from where I bought it and I spoke to the original owner and he was a super guy, and could not praise the amp enough. I did read the reviews online and that was another factor that pushed me to buy it. I do like that Cary sound, hence my pre-amp.

Do you think tubes can do enough to change the sound or am I trying to make a purse from a pigs ear?

Currently I have my Aleph's back online, this is actually the 2nd tube amp I have purchased and the 1st, Jolida 102b, has been sitting in a box for about a year. I have to send it back due to 1 socket basically burning out every tube I put into it. I'm beginning to think I should stick with SS and understand why tubes are so niche.

Anyone interested in a AES Superamp or a fixer Jolida 102b

Jack

[sebrof]

I almost hesitate to post this because it's so darned obvious - You bought a used amp and you have no idea the condition of the power tubes. They wear out. Maybe they are spent.
Do you have access to a way to test the tubes, or a quad of known good tubes?
Also - Did you check/set the bias of the tubes?

My gut tells me that although you might not prefer the Cary, if it's functioning correctly I doubt you'd find it thin and light vs. the Alephs.

[fz1jmp]

I'm way out of my league here !!!

I figured, let me call AES, well Cary and just ask them about this amp. I spoke to a very very knowledgable person, Dave. I gave him my serial num and he said, hummmm, that has a bunch of tweaks you did not see on later models. So, 3 things I have no idea what he was saying;
1. It had a bias adjustment screw on the back, even though its auto-biasing. Well there is also a input jack, which I thought was a headphone input! TUrns out thats where you check the bias current! Can I use a simple voltmeter? He said he should be about 120mv, 30 X 4, I got that. But then he said use the 200mv scale?
Can I just turn it all the way counterclockwise and slowly turn it as I listen?
2. The review says it used 6922's, not the 6550's? Huh? Can I replace the 6550's with 6922's?
3. What the heck is the difference between tetrode and pentode mode? And sound?

I hope I'm not reaching with these questions, I would love to hear what this amp can do, I don't think I am.

[fz1jmp]

I almost hesitate to post this because it's so darned obvious - You bought a used amp and you have no idea the condition of the power tubes. They wear out. Maybe they are spent.
Do you have access to a way to test the tubes, or a quad of known good tubes?
Also - Did you check/set the bias of the tubes?

My gut tells me that although you might not prefer the Cary, if it's functioning correctly I doubt you'd find it thin and light vs. the Alephs.

Sometimes the obvious is what bites you in the a$$, and ahem, you may be right. No, I took the persons word who I bought it form. Now, it was not a typical no talk transactions. I spoke to this guy for hours and he was a true joy to chat with. Now, he may not actually know what the shape of the tubes were in. I actually don't think I thought of that.

Anyone near Westminister, MD. or lets just say Baltimore, MD. with a quad of KT's interested in either selling or loaning? Maybe thats what I should try. I honestly don't want to give up on this.

[Early B.]

It's wired in pentode mode as opposed to triode mode also, I'm not sure if that matters.

This may be the source of your problem. The difference in sound between these two modes is usually quite significant.

[Quiet Earth]

1. It had a bias adjustment screw on the back, even though its auto-biasing. Well there is also a input jack, which I thought was a headphone input! TUrns out thats where you check the bias current! Can I use a simple voltmeter? He said he should be about 120mv, 30 X 4, I got that. But then he said use the 200mv scale?
Can I just turn it all the way counterclockwise and slowly turn it as I listen?

2. The review says it used 6922's, not the 6550's? Huh? Can I replace the 6550's with 6922's?

1. If you are measuring 120mV then yes, the 200 mV scale is correct because that is the max voltage you would read at that setting and gives you the best resolution. It sounds like you followed the verbal directions correctly to me and the 6550s are biased right. You did good.

2. 6922s are input tubes and they are compatible substitutes for ECC88 which is the British designation for 6DJ8. You have the correct input tubes in there. I think you are just confusing yourself right now, which is totally understandable.

You should call the seller back just to ask him if he thinks a re-tube is in order due to age of tubes (. Not sound quality )

[Quiet Earth]

This may be the source of your problem. The difference in sound between these two modes is usually quite significant.

Not only that, but a push pull pentode amp is not typically what one would choose if warm and lush is the goal. Especially 6550s, IMO.

YMMV of course, and all pentodes are not created equal, etc.