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 Post subject: Re: Tube Rolling
PostPosted: July 11th, 2015, 4:09 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 159
There are various grades os the Psvanes. Even the standard grades would be a step up from stock Chinese, IMO. The Genelex seem like a good buy, though. They are well-made. Let us know how they sound. I'm very interested to know if they improve things significantly.


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 Post subject: Re: Tube Rolling
PostPosted: July 11th, 2015, 4:38 pm 
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Grover Gardner wrote:
There are various grades os the Psvanes. Even the standard grades would be a step up from stock Chinese, IMO. The Genelex seem like a good buy, though. They are well-made. Let us know how they sound. I'm very interested to know if they improve things significantly.


You also mentioned changing out the 6SN7's with Psvanes, would the standard grades offer any advantages over the Sylvanias?

I'm getting the Genalex tubes on Monday, and I will make a post after I get them running. Yen Audio told me they have better tone, which sounds like it would be a good match with my speakers because I have spent a lot of my efforts in speaker building focusing on tonal quality. They also told me they have good frequency response, but I'm not sure what exactly that means: extra High/Low extension? Good balance between the extremes? I don't know. It's kind of vague, but I hope it's a good thing!

Chris


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 Post subject: Re: Tube Rolling
PostPosted: July 11th, 2015, 6:47 pm 
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Joined: October 21st, 2013, 6:53 pm
Posts: 270
Roscoe Primrose wrote:
:character-oldtimer: Like J-Rob said, listen to it for a while as-is. Tube rolling should be the very last thing you go for, getting the right amp (or the amp right) is much more important. Think of an amp like a woman, a really good design is like a beautiful woman, a lousy design is like an ugly woman. Tube rolling/boutique parts are like makeup. A beautiful woman is still beautiful without any makeup, and no amount of makeup can make an ugly woman beautiful....

As for the low-end, that's a tough one with tube amps unless the transformers are up to it. At that price point, the transformers can only be so good... :whistle:

Roscoe

Hey Roscoe, You have to remember: I'm using 7 inch woofers, not 18 inch woofers. I'm no expert but I don't think my transformers are going to have problem moving a 7 inch woofer 1 or 2 millimeters. It's a fundamental difference between your approach and mine. As far as I can ascertain, your approach is that displacement is everything, which sounds pretty rational with the typical understanding that sound is basically made up of frequency and magnitude. I have a pretty interesting twist on that. It's a cool difference between your approach and mine, and it would be fun to talk about if you want to entertain me.


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 Post subject: Re: Tube Rolling
PostPosted: July 12th, 2015, 3:32 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 159
Roscoe has a point in that the build quality of the amp is necessarily going to largely determine what you can get out of it,. OTOH I think that quality tubes could improve the situation. Yes, I think the standard Psvane 6SN7s would offer more of what you're hoping to hear, which I take to be a fuller picture of the music. But wait and see what the Genelexes do before you go any further.


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 Post subject: Re: Tube Rolling
PostPosted: July 12th, 2015, 5:52 pm 
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Joined: October 21st, 2013, 6:53 pm
Posts: 270
So what is the difference between a good transformer and a not-so-good transformer?

Aren't they just a bunch of coiled up wires?

Isn't the only significant difference between one or another the size, or output capability, which is primarily determined by the size?

Would it really matter driving something as small as a 7 inch woofer? I'm not talking about a small diameter subwoofer that still would require a large excursion and lots of power. This is a midbass driver doing double duty. Even during some of my lowest loudest recordings, I can put my finger on the surround, and it's barely moving! My meters barely crack a single watt!

My theory is that my Bass criticism has more to do with tonal richness than it does with power or excursion. It's not a quantity issue. I like to think of it as an "intensity" issue. My speakers still make lots of low, relatively loud bass with this amp. I just think that, without changing any magnitudes, the signal could be richer in tonal quality, which most people would identify as "better bass". The interesting thing is that I don't think that means the signal is any lower, or louder. It just sounds better!

The funny thing is that I'm actually very happy with this amp! It does a lot of things exceptionally well considering the price I paid for it! I just recently had a much more expensive solid state amp that did one or two things a little bit better, and I was only curious if I could spend a little extra money and swap out some tubes to bring out those qualities I liked in the other amp.

Thanks for all the good advice so far!

My Genalex tubes come tomorrow.

Chris


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 Post subject: Re: Tube Rolling
PostPosted: July 12th, 2015, 8:23 pm 
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If you want to get a good primer on audio transformers speak with David Berning. In reality it is very difficult to make a good output transformer especially with single ended amps because in those cases there is a considerable amount of DC in the core. Push pull amps like you have are not as great a problem but there are still many design tradeoffs to be made that involve leakage inductance, stray capacitance, etc.. If you design a transformer to provide good low frequency response it will probably have to compromise high frequency response and satability. Using feedback and other frequency selective tweaks to prop up a bad transformer inevitably leads to poor performance. That is why David developed the ZOTL to eliminate output transformers. It is not the same as conventional OTL amps or hybrids using solid state output drivers. Check out this link:

http://davidberning.com/technology

As far as what you are hearing I would guess it is more related to frequency response changes caused by the output impedance of the amp reacting with varying input impedance of the speaker. If the amp has inherently poor flatness of frequency response it could also add to the problem. Both conditions can be tested.

The size of the driver is really not material. Rather the sensitivity, that is the ability to convert electrical power into acoustical power is the deciding factor on how much power the amp will need for a given SPL for a given size room. If the response of the driver falls off from nominal at any frequency, that is the response flatness is poor more power will be needed with EQ to bring the response back up. That is a gross oversimplification but fundamentally describes the situation.

Tom


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 Post subject: Re: Tube Rolling
PostPosted: July 12th, 2015, 9:55 pm 
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Joined: October 21st, 2013, 6:53 pm
Posts: 270
tomp wrote:
If you want to get a good primer on audio transformers speak with David Berning. In reality it is very difficult to make a good output transformer especially with single ended amps because in those cases there is a considerable amount of DC in the core. Push pull amps like you have are not as great a problem but there are still many design tradeoffs to be made that involve leakage inductance, stray capacitance, etc.. If you design a transformer to provide good low frequency response it will probably have to compromise high frequency response and satability. Using feedback and other frequency selective tweaks to prop up a bad transformer inevitably leads to poor performance. That is why David developed the ZOTL to eliminate output transformers. It is not the same as conventional OTL amps or hybrids using solid state output drivers. Check out this link:

http://davidberning.com/technology

As far as what you are hearing I would guess it is more related to frequency response changes caused by the output impedance of the amp reacting with varying input impedance of the speaker. If the amp has inherently poor flatness of frequency response it could also add to the problem. Both conditions can be tested.

The size of the driver is really not material. Rather the sensitivity, that is the ability to convert electrical power into acoustical power is the deciding factor on how much power the amp will need for a given SPL for a given size room. If the response of the driver falls off from nominal at any frequency, that is the response flatness is poor more power will be needed with EQ to bring the response back up. That is a gross oversimplification but fundamentally describes the situation.

Tom


Thanks Tom, I looked at the link. It's interesting but probably a little beyond my capabilities.

The bottom line is that I'm planning on keeping the amp, for the most part unmodified. I don't really have a complaint. It's more like just a simple observation of the difference between this one and my previous, much more expensive solid state amp. It might be nice to gain back some of the qualities I was used to with the other amp, and it seems to me that it should be a relatively simple thing to do, especially given that fact that I have a lot of different tubes I could swap out to experiment. It could be like Roscoe says, that I'm limited by the design of the amp, but I'm really only trying to achieve a couple relatively subtle changes! I'm not trying to rework the performance of the amp. I just want a little bit more "airiness" in the highs, and a little bit more tonal richness in the bass. It's so subtle in fact that I previously would have resorted to fooling around with cables and fuses to achieve it. Through previous experiments though, I have gathered the best cables I could find, so I don't think there is much more fooling around in that area for me to do. My speakers are at their pinnacle too! There is really no variable left that I can think of that I didn't already manipulate and optimize!

If I can't achieve it with a couple of tubes, then everything is probably going to stay the way it is.

Chris


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PostPosted: July 13th, 2015, 5:00 pm 
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Joined: October 21st, 2013, 6:53 pm
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Got the Genalex tubes this afternoon. I have been listening to them for several hours.

First thing I noticed was the voices. They have more depth, richness, and detail.

Then I noticed that the whole soundstage as a little bit deeper.

Bass tones were a little bit richer. String Bass for example was very clear and unmistakable. You could actually hear the details of the whole instrument, not just a vague Bass tone!

Percussive Bass sounds (Bass Drums mostly) were a little more intelligible, and had a little bit lower ring to them.

It appears that it was general improvement in fidelity across the board

Highs seemed a little bit more forward, but still rolled off to some degree. It's not the actual sounds, but the complex directional cues that are hidden in the HF that seem to be missing. The example of standing in the doorway at the Orchestra instead of the middle of the hall still seems to stand.

The other thing I noticed pretty quickly, was that even though the audiophile effects I was looking for seemed to be there, I had a little bit of a loss of connection with the Musical/Emotional content of the recordings. A friend of mine refers to this as sounding "Clinical". It was strange, but it seems to be fading as I proceed through more recordings. I have not returned yet to some of the initial recordings I heard it the most in, but I will eventually and we will see what happens. I bought a Cambridge CD player a couple years back that gave me that experience too, and it was so bad that I had to beg the stereo store to let me return it the very next day. This clearly doesn't bother me as much, and since it seems to be fading, I'm certainly not going to fork out more money for four more tubes to try and fix it when there is no guarantee that that would even work, and I don't want to go back to the Shuguangs.

Overall I think I'm pretty happy! I would probably recommend them over the Shuguangs to someone with an amp like mine. i'm not so thrilled with the fact that I had to $150 for them, considering the other Russian tubes only cost $80, but they guy told me they were better so I took a chance!

Thanks for all the advice and other information!

I hope this post is in some way useful!

Chris


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 Post subject: Re: Tube Rolling
PostPosted: July 13th, 2015, 5:38 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 159
Break them in for 50 hours or more. They'll go through some changes.


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 Post subject: Re: Tube Rolling
PostPosted: July 13th, 2015, 5:43 pm 
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Joined: February 28th, 2013, 10:38 am
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chris1973 wrote:
Hey Roscoe, You have to remember: I'm using 7 inch woofers, not 18 inch woofers. I'm no expert but I don't think my transformers are going to have problem moving a 7 inch woofer 1 or 2 millimeters.


An 18" woofer isn't, necessarily, any harder (or easier) to move/control than a 7" woofer.....

Roscoe


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