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Tube Rolling 12au7, 12ax7 (Read 96028 times)
surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #100 - 05/07/22 at 00:44:49
 
I wholeheartedly agree with you that adding extra input voltage adds weight to the music.

My current SUT has step up ratios of 5x, 10x, and 20x. When I purchased my 0.5mv cartridge all of my research and calculations pointed to a 10x step up ratio to be optimal - giving 5mv of output, but surprisingly it wasn't.

The 20x step up ratio combined with my low DCR 0.5 mv cartridge took my listening experience to an entirely different level than what I was accustomed to with previous upgrades. The music took on a life of it's own and there is no going back for me.

This is the main reason I have decided to purchase the ZP3 because I think it will be a perfect compliment to my current set up.

I am just a little worried about the extra 2db in gain over my existing phono stage (+40db)....but maybe the magic of tubes will compensate for the extra 2db in gain?

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Archie
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Re: Tube Rolling 12au7, 12ax7
Reply #101 - 05/07/22 at 01:03:06
 
What do you think the downside of the extra gain is?  My experience is that more gain will result in more volume for the same knob position.  With 1 volt input, most of the Decware amps won't be able to reach full power/volume.  And of course, if input exceeds the amp spec for full volume, the input is attenuated by the amp volume knob.

But I may not understand your issue.  I've always thought the ZP3 would benefit from more gain but after reading Steve's White Paper on the development, I think he was happy to get what he got without noise.
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
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surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #102 - 05/07/22 at 12:38:30
 
If I had all tubes in the signal chain I do not think I would be having any issues with the extra gain.

The problem is that I do not think my solid state integrated amp can properly handle the extra gain.

When I increase the gain of my current phono preamp above +40 db, the sound definitely worsens because there is too much gain.

From what I have read on this forum and others is that if one uses 5751 tubes in place of 12ax7 tubes, the total output should drop by around 3 db, but I do not know if this same db drop can be applied in the case of the ZP3?

And I do not know if this 3db is being calculated or if it is just a rule of thumb measurement derived by knowing each incremental adjustment of most volume knobs is around 3db?
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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #103 - 05/07/22 at 14:31:38
 
Two questions to ask in these situations are: what is worst case? Which is not informative by itself, so we ask: for what duration?

Through much reading of data provided by Sure Bros. and others, at 1,000Hz the absolute limit in vinyl cutting is 35 cm/s. Reading further, the max found through measuring of many records was ~ 28-30 cm/s, at some place on two records (of many samples). Aside those two, the highest were ~ 12 and 15 cm/s. For a cart output measuring.0005 V (.5 mV) @ 5 cm/s-1,000 Hz, 30 cm/s is 6x and 15 cm/s is 3x above test spec. From an article I dug out from Stereo Review printed in 1968, the writer said that few records have anything much above 15 cm/s. So I have taken for myself that 4x the test record spec is the R/L actual worst case that we should have any concern about.

With a cart of .5mV going into a 20x SUT and a 125x (42 dB) phono pre, that comes to 5V. Worst case.

The second question is duration of the event. Look at the data on this page: https://www.dpamicrophones.com/mic-university/acoustical-characteristics-of-musi...

The attack duration of snare drum measured 5-8ms, bass drum:8-12 ms, tympani (all sizes): 10-18 ms, trumpet: 20-40 ms. These are the loudest instruments in the orchestra. 20 ms is 1/50 of a second. That would be nigh impossible to attract perceptual notice, for one, and I don't think it would trouble even a SS preamp input stage overly much. I don't know for certain, but I don't think even 50 ms (1/20th second) would cause too much trouble, but who knows.

So then with your cart and SUT, we have "an extraordinary vinyl event" resulting in 5 volts output of a 42dB phomo preamp for 5-40 milliseconds.

After all that, your own experience is the final determinant. If you notice distortion when you set the phono preamp higher than 40 dB, then there it lies. But that might or might not occur with another phono pre, SS or tube.

I don't think you need to stress much over it because it might be fine with the ZP3 as is, and if not you have the option of replacing the 12AX7 tubes with the 5751 set.


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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #104 - 05/07/22 at 15:11:36
 
To this-

Quote:
From what I have read on this forum and others is that if one uses 5751 tubes in place of 12ax7 tubes, the total output should drop by around 3 db, but I do not know if this same db drop can be applied in the case of the ZP3?


The discussion of 5751 tubes earlier in this thread was specifically in reference to the ZP3. So, yes.

Quote:
And I do not know if this 3db is being calculated or if it is just a rule of thumb measurement derived by knowing each incremental adjustment of most volume knobs is around 3db?


It was calculated. Amplification factor and gain are two different things, but indirectly related and close enough for this discussion. The 12AX7 has mu of 100, the 5751 has 70.  Log(70/100) x 20 = -3dB. Theoretically, this would change gain of the ZP3 from 42dB to 39dB, or from ~ 125x to ~ 90x.
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Archie
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Re: Tube Rolling 12au7, 12ax7
Reply #105 - 05/07/22 at 17:21:27
 
Edsonic is lightyears ahead of me in his understanding of all of this but this quote stands out:

Quote:
After all that, your own experience is the final determinant. If you notice distortion when you set the phono preamp higher than 40 dB, then there it lies.


All of the analysis aside, you say you get distortion above your 40dB.  Is it in your existing phono pre?  My NAD pre has both MM and MC inputs but the MC is crap.  (I don't use this anymore though.)
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #106 - 05/07/22 at 17:57:53
 
What he said was:

Quote:
The problem is that I do not think my solid state integrated amp can properly handle the extra gain.

When I increase the gain of my current phono preamp above +40 db, the sound definitely worsens because there is too much gain.


So it looks like his phono preamp, when set above 40dB, is sending out more than his SS integrated amp can deal with.

His calculations are correct that a .5 mV cart through his 20x SUT and the ZP3 should produce 1.25 V output.

Louder portions of a record (not the few extremes) might result in 2x or 3x that. The Decware CPS3 starts overloading at ~ 3.32 V (if I remember correctly) with the input attenuator full open. If his integrated does not have adjustment for input level (likely not), then 3.75 V or even 2.5 V might be a problem.

Addendum: Thinking over that last item, I don't know what phono preamp he has currently, but it is indeed possible that it sounds worse at a 42 or 44dB setting than at 40dB.
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Archie
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Re: Tube Rolling 12au7, 12ax7
Reply #107 - 05/07/22 at 18:08:34
 
More things I am ignorant about.  I assumed that anything with a "volume" knob would attenuate the input signal down to zero.  There must be a knob on his amp otherwise it'd play at full volume always.  What am I missing?
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.
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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #108 - 05/07/22 at 18:23:51
 

First of all, I added to my previous post, so have a look.

To your question above- keep in mind that the CSP3 has three different level controls; input, volume, and output. Many preamps and I'd bet all integrateds do not have an input attenuator. The preamp volume knob controls the amount of gain.
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surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #109 - 05/07/22 at 18:24:47
 
Hi guys, I appreciate all of the helpful information and feedback.

I now believe the main culprit of the issue I am hearing is what Edsonic mentioned - "extraordinary vinyl events"

My integrated amp and/or phono preamp is not properly handling the "extraordinary vinyl events" that my 20x SUT and 0.5mv cartridge and phono preamp are producing. Events lasting only in milliseconds with output ranging from 2 to 5 volts.

I have two technical follow up questions I hope you don't mind answering-

1. Do you think the maximum input capacity of the ZP3 increases when using the lower mu 5751 tubes? Edsonic - I read one of your other posts where you thought the ZP3 should have at least a maximum input capacity greater than 100mv. Will the use of 5751 tubes increase this maximum capacity number?

2. Edsonic - your calculated db decrease of the 5751 compared to using the 12ax7 was Log(70/100) x 20 = -3dB. Does your calculation encompass the use of 5751 in both v1 and v2 slots? Or is using 5751 tubes in both v1 and v2 slots additive to the drop in db? [Log(70/100) x 20 + Log(70/100) x 20] = -6.19 db for an overall output of around +36db?

thanks for your help
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Archie
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Re: Tube Rolling 12au7, 12ax7
Reply #110 - 05/07/22 at 19:02:15
 
Quote:
The preamp volume knob controls the amount of gain.


Sorry if I'm taking this thread off topic but this is very interesting to me as I've never heard an explanation of what happens when a signal is inputted to an amp.  Also, I've never understood what really goes on with the 3 adjustments of the CSP3 and how they are different.  I thought the input and output settings were a sort of maximum with the Master Volume attenuating from zero to that maximum.

My assumption in my above post was that the amp (Decware anyway) attenuates the input signal from zero to it's actual value -- if the amp doesn't distort before reaching it.  If this doesn't happen then what does?
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.
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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #111 - 05/07/22 at 19:13:49
 
Surfer-

Refresh page and make sure you read the last few items Archie and I talked about. We all might have been typing at the same time.

To your first question above- I can't say for certain. I just know the basics about tubes so I don't think I'm qualified to answer that definitively. I know that 12AX7 tubes overload easier than tubes with less gain, generally speaking. In any case I don't think any cutting levels are above ~ 52-55 cm/s, that occurring at 8kHz-9 kHz. I don't know how to mathematically translate cartridge output from 5cm/s @ 1,000 Hz to other frequencies.

Have a look at this:http://pspatialaudio.com/max_velo.htm Scroll to the chart halfway down the page, past the graph.

My guess about the ZP3 input limit was based on a 'search survey' which brought up several SS phono preamps with 70-120 mV limits and an AR and Manley Chinook w/ 240 mV limits. My estimation of at least 100mV for the ZP3 is probably a low ball figure. That said, there are a number of phono preamps with 40-60 mV limits.

To your question about 2 tubes / 2x the dB calculation, I'm not sure about that either. Standalone, it makes sense, but the circuit might have it otherwise.
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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #112 - 05/07/22 at 19:59:31
 
Archie-

I only know the bare basics of electronics- Ohm's Law, how to express watts in those terms (V²/R), RMS/peak/p-p, how to calculate gain, etc. I just know how to run the numbers -  the inner workings of circuits, not so much.

I was told by the instructor in my Studio Recording class and by a sound company owner I worked for sometimes (eons ago, both cases) that the 'pad' (input attenuator) determines the level of input, and the fader controls the amount of gain. Input levels are set with the fader at unity gain.
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surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #113 - 05/07/22 at 20:55:30
 
Edsonic and Archie,

I appreciate the knowledge you have shared with me. I definitely have a better understanding of how much voltage my phono preamp and integrated amp are experiencing even if for a few milliseconds.

When my ZP3 arrives later this year I will be sure to add my experience of how well a ZP3 with various tube compliments works with a 0.5mv cartridge and 20x SUT.

and fyi - my integrated amp does not have an input attenuator, only a volume knob

And in the meantime, if anyone knows if swapping the two 12ax7 tubes for 5751 tubes theoretically reduces the gain by 3db or 6db, please do not hesitate to respond:)

Thanks again

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Archie
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Re: Tube Rolling 12au7, 12ax7
Reply #114 - 05/08/22 at 00:56:49
 
Quote:
and fyi - my integrated amp does not have an input attenuator, only a volume knob


My problem is that I thought these were the same thing.
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.
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Edsonic
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Re: Tube Rolling 12au7, 12ax7
Reply #115 - 05/12/22 at 13:20:58
 

A few things I overlooked in prior discussion.

Surf, I think the reason your SUT sounds better @ 20x setting is because the cart DCR is so low. (Generally speaking, lower cart DCR is a good thing). The SUT steps down the input impedance of the phono preamp by the square of the  turns ratio. So from the 47kΩ input of the phono pre  a 10x ratio would present 470Ω to the cartridge, 20x ratio would make it 117Ω (47k/400). With a cart DCR of 1.4 the second number is a much better fit.

Regarding the gain situation, I think it might be best to have the ZP3 operating as intended to the extent possible. To that end using an in-line attenuator between the phono pre  and the integrated might be just the ticket. (I knew there was something kicking me in the back of the head before, that was it). Here are some from Parts Express -

https://www.parts-express.com/home-a-v/audio-video-accessories/line-level-attenu...

They are cheap enough that you could get both the 3dB and 6dB pairs. I searched around a few years ago and these seem to be well regarded. They should be plugged into the 'line in' / 'aux' of the integrated to keep the signal strong till the end, for better signal vs. EMI/RFI on the cables. That last item is another reason the attenuator pair  might be a better solution than lowering the signal output of the ZP3 by use of lower gain tubes.

If you still want to try the 5751 somewhere I think it should only be after the RIAA section. (Another thing I forgot about). The front tube of the ZP3 is where the signal comes in first. Using the 5751 there would  provide less gain to a weak signal then going through the however slight noise of the resistors and capacitors of the RIAA filter. So then worse signal-to-noise ratio at the worst place.

I think using the 5751 tube in the second slot, after the RIAA, should be okay, in the process obviating the need for our question about dB using two 5751s. If you eventually get into tube rolling you might pay the extra money (for the front tube) to get 12AX7s that are tested for low noise. Vintage Tube Services and Brent Jessee Recording & Supply do that, there might be others.  

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surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #116 - 05/12/22 at 16:56:41
 
Edsonic -

Your advice and suggestions are much appreciated!

The 3db or 6db in-line attenuators sound like the most cost effective approach to addressing my excess gain problem.

Although, now considering I can add the 12ax7 and 3db or 6db attenuators to the mix of different tubes I now have in my possession, and if my calculations are correct - the number of possible tube/attenuator combinations has jumped from 56x [5!(8-5)!] to 462x [6!(11-6)!]......I guess this is a good problem to have....:)
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surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #117 - 01/16/23 at 13:58:13
 
Hi guys,

Hope all is well and happy New Year!

While I am only a few months away from receiving my ZP3, I just wanted to share a few updates.

Although I still think my current phono preamp is experiencing voltage spikes beyond what it is capable of handling, I discovered the primary problem…..my integrated amp's DC bias was measuring far above required specs. (About 200% above spec!)

Once I turned down the DC bias to the specified level found in the service manual, a lot of the issues I was having with my vinyl rig playback went away.

So, I am happy to say I will probably not be needing any type of attenuation in the way of in-line attenuators nor lower output tubes.

Once I have spent sufficient time with the ZP3 and done some tube rolling, I will report back here

Cheers
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Sean
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Re: Tube Rolling 12au7, 12ax7
Reply #118 - 04/28/23 at 01:10:18
 
Dredging this one up from long ago. It's got tons of great info in it, most I'm still trying to process.

My current setup is Mofi TT w/ AT OC9 III to a Ned Clayton 1254 Cinemag SUT to ZP3 to SE84UFO. All RCA is Mogami 2497. SUT is grounded to both the table and ZP3. The AT OC9 is .5mv. The SUT has switches for 1: 10, 13, 20, and 40. My previous SUT was 1:15. 13 is a little lacking while 20 is LOUD. Before, I listened with the volume between 25 and 50%. On 1:20 the volume rally sees 25% and at 25% it seems louder than what 50% gave me with the other SUT.

It could be there's just a whole lot more music coming through now, like right up in your face, wall to wall, floor to ceiling the room is gone and I'm sitting 6' from the band.

So what's that have to tube rolling? Well, I have a pair of Raytheon windmill getter 5751's. Bought them for my previous phono pre as attempt to tame it's gain. They worked there. On the ZP3, as talked about above, I find the 5751 a no go in the middle (RIAA). The whole bottom end just collapses. I do like them in the first spot, vocals seem much more lifelike with the Raytheon.

The past few nights I've been trying different 12AX7's in the middle. Current resident there is a Mullard (The Fisher label). Tonight I'm going to try a red tip Sovtak 12ax7LPS. As for the 12au7, I don't have many to choose from because in a moment of stupidity I sold a tube pre with all the 12au7's I had. Anyhow, I've got a Gold Lion gold pin in now. That tube has bested a GE 12AU7A short black plates and GE 5814A triple mica 12AU7A. Someone mentioned a Siemens 12au7, I had a few Siemens I really like in another amp, holy moly those are now some VERY expensive tubes.
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Mofi StudioDeck, AT OC9III, Cinemag 1254 SUT, ZP3, CSP2+, SE84UFO, Tekton Pendragon

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Sean
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Re: Tube Rolling 12au7, 12ax7
Reply #119 - 04/28/23 at 21:43:49
 
After some reading I went way way way down the wrong road all the while convinced it was correct. .5mv cart on 1:20 = 10mv!!! No wonder things were too loud. 1:10 is a better setting at 5mv. The volume knob now gives me the range I was used to. I removed the 5751 from the first spot and things became even better. I really love the smoothness and openness of the 5751's but I really think the .70 output from them limits the overall performance.

I didn't care for the Sovtek red tip 12AX7LPS. Bit too sharp for my tastes. Settled on the following:
1 - Mullard 12AX7
2 - RCA 12AX7A
3 - Gold Lion 12AU7

Now that the 5751's are out, I have to go back and try those 5184a's in the 12AU7 spot. If anything is missing, it's on the low end.
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Mofi StudioDeck, AT OC9III, Cinemag 1254 SUT, ZP3, CSP2+, SE84UFO, Tekton Pendragon

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Sean
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Re: Tube Rolling 12au7, 12ax7
Reply #120 - 05/02/23 at 02:46:46
 
Still at it. I found a box I forgot about with some tubes. These either came out of a jukebox or console, I really can't recall.

1 - RCA 7025
2 - RCA 12AX7A
3 - GE 12AU7A

I'm happy with the first two spots, the 12AU7 I'm still fooling with. So far the Gold Lion is my favorite.

They ain't pretty, but they are very dynamic. Just noticed I'm running all RCA tubes minus the 12AU7.
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surfers5
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Re: Tube Rolling 12au7, 12ax7
Reply #121 - 08/09/23 at 18:44:26
 
Hi everyone and hope all is well!

I have spent several months with the ZP3 and feel like I can now offer some personal feedback which hopefully someone will find useful.

I am extremely happy with the ZP3 and its numerous tube rolling possibilities which can change the sound to your optimal preference for not only different music genres, but for each album, and I could go as far to say each song if not for needing to change the tubes too frequently.

I think it would be best to disclose my current set up first, which is a mix of budget components from the 70’s and more esoteric Japanese and European components which were all purchased in the used market:

Receiver – Sony STR-V4 (55 wpc)
Speakers – KLH Model 23 – (around 87 db per watt sensitivity)
Turntable - VPI Prime Scout
Phono Preamp – Decware ZP3
Step Up Transformer – Music First Audio SUT V1 Copper - 5X, 10X, or 20X turns ratios – 1.3 ohm impedance of primary coil measured at 1 khz
MC Cartridge – My Sonic Lab Gold Signature – 1.4 ohm DCR

**The 1.4 ohm DCR of the MC cartridge and 1.3 ohm impedance of the primary coil of the SUT is almost a perfect match, which allows for maximum performance across the widest range of frequencies – common knowledge is that you must pair an MC cartridge/SUT based on optimal voltage gain and on optimal loading, but the not discussed critically important X-Factor for ultimate cartridge/SUT pairing is the proper matching of the internal impedance of the cartridge and the SUT’s primary coil impedance. The Japanese tend to adhere to this X-Factor much more than their American and European counterparts**

My previous phono preamp was a Musical Surroundings Nova set at +40 db of gain. This solid state phono preamp is a great phono preamp I can highly recommend with very tight and deep bass and quite a deal on the used market for around $500 USD.

With the ZP3’s higher gain of around +42 to +43 db, I did have to decrease the gain of my Music First SUT from my usual 20X down to 10X. The resulting gain going into the ZP3 was decreased to 5mv from 10mv.

I would say that the overall performance gain with my SUT set at 10X with the ZP3 with stock tubes was a +20% increase in performance compared to my SUT at 20X with the Musical Surroundings Nova.

In the world of high-end audio we all know an increase in performance of 20% is huge and could potentially cost a large amount of money, so I was extremely happy with the ZP3 and the long wait was well worth it.

But…..there was some magic I was accustomed to hearing missing from some familiar tracks……

Because of the KLH speakers lower sensitivity of 87 db, they really need a lot of voltage to make them sing and on a few songs when I was able to increase my SUT to 20X going into the ZP3, the sound was out of this world – like technicolor rainbows of beautiful sounds pouring into the room and over your body like a lucid dream….yes, I know this description is over the top, but this is the best way I can explain what I was hearing with my SUT set at 20X. I felt like the tubes in the ZP3 were thanking me and were completely able to run free without any limitations producing ultra-vivid and dynamic music without boundaries….

But, with the ZP3 and stock tube configuration I could only turn up my SUT to 20X on a few tracks that were already cut quiet….

This is the point when I started experimenting with NOS tubes. I thought placing a 5751 in the V1 spot might tame the gain enough to allow for me to turn up my SUT to 20X, but it wasn’t. I kept having to turn down the gain to 10X for some songs to play without excessive gain.

I then tried a 5751 in the V1 spot and a 5751 in the V2 spot. This combination did not work well at all. It sounded as if 20% of the life of the music had been sucked out of the room.

I then tried an even lower gain 12AT7 in the V1 position and 12AX7 in the V2 position with my SUT set at 20X…….Voila!!! technicolor daydreams were pouring out of my speakers and the sound was nothing short of a religious experience. ….I know, another over the top description, but this is how I felt on an emotional level.

Another increase in performance was had by replacing the 0A3 voltage regulator tube with an 0D3 voltage regulator tube. The best way I can describe the improvement in sound was that the 0D3 was giving much more space in the sound stage from back to front and side to side for the music to flow. I think this was because of the extreme dynamics being produced by the My Sonic Lab cartridge and SUT at 20X combination needed this extra breathing space to run at their optimally combined musical speed.

At this point, I thought to myself that the performance of the ZP3 is now 100% - 300% + better than my previous phono preamp - the Musical Surroundings Nova - depending on the album being played.

But…. I have noticed that a few rock & roll tracks that were cut really hot are pushing the limits of gain and I have ordered some 12AY7 tubes to put in the V1 spot to see if this will do the same trick as the 12AT7 did with most of the music I play.

Special note – after reading Sean’s previous posts and seeing that he is using Tekton Pendragons speakers with a 98 db per watt sensitivity – I think the reason I can run my SUT at 20X with the My Sonic Lab’s 0.5mv output for a resulting gain of 10mv is primarily because of the KLH speakers being less efficient and only having an 87 db per watt sensitivity.
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