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older TL Audio dual valve mic pre Single-Channel Preamps
Old 20th December 2010
  #31
Quote:
Originally Posted by Retromod View Post
Hey Puffer, I think you took me the wrong way. I am in no way sniping at your advise on tube rolling. In fact I have many 12ax7's that I got at a bargain as well and strongly encourage anyone to experiment with different tubes without spending a lot of money. I am merely suggesting an alternative to the often overpriced famous name 12ax7's that I have so often heard people talk about dropping several bucks on.
The reason I suggested NOS 12at7's is that if you want critical stereo matching, it is important to have a fairly well matched pair and if they are brand new from the same batch, they are more likely to be within the same tolerance and character.
Mullards happen to be wonderfully consistent and unfortunately as a result, are often pricey.
I have tried many re-issues and I have yet to be satisfied with the results.
thumbsup Cool. I was afraid the conversation was going to turn to some place where tubes are this dark, alchemical art form, shrouded in mystery... which is sort of true, but only because we are in an age that for the most part has stepped away from the use of tubes in most areas of electronics. And I do not say ANY of this the breadth of knowledge that many other electronics buffs on here have. I am learning just like everyone else. But I have seen some silly things written on here regarding tubes and I like to make sure if it's a conversation I am involved in, that I do my best to set the record straight.

With that spirit in mind, I should say again but with better specificity, that of course you can drop a 12AU7, 12AT7, 12AY7 into the same spot where the manufacturer calls for a 12AX7--the difference is the gain each of those tubes will produce.

Yes, you are quite right regarding the need for matching tubes in these dual channel tube preamps if the user ever hopes to do stereo work.

And yes, my experience is similar to yours in that I have found the NOS tubes I have used are better in pretty much every way compared to the new production tubes I have bought and used. But I simply can't afford to have NOS bottles in every tube position for the different things I own. But in the case of the tube mic preamps, I definitely try to drop in the very best tube I can afford as the sound obviously depends upon the tube.

Anyway, sorry if I jumped on your comments too hard there. In truth, I really appreciate you adding to the conversation. That's what the threads are all about on here--sharing our knowledge and hopefully helping each other out. And it is good to hear, see, read other ways to do things.
Old 22nd April 2012
  #32
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Basslik's Avatar
 

Quote:
Originally Posted by Puffer Fish View Post
I have read a lot of TL Audio bashing on here. Unfortunately, I read most of it AFTER I picked up an older Dual Valve mic pre. It is one with the slate gray front, so it's even older than the blue front version of the same product. Anyway, all the bashing had me a little worried, because at that point it was in the mail on the way to my house...

I tried it out and... not so bad. Not great, but not bad. It has two 12AX7s in it: one for each channel. Through the mic pre you use one side of the tube and through the D.I. you use both sides of the tube. Anyway, my studio colleague and I did some A/B'ing with it the other day.

I picked up a set of NOS Sylvania 12AX7s. Since the pre has two identical sides, I swapped out one of the stock tubes (an Edicor 12AX7, which I never heard of before) with a Sylvania and left one of the stock tubes in the preamp.

EVERYTHING we ran through the box sounded night and day different/ better with the NOS Sylvania. I expected a difference, but not such a significant difference. Wow. It was like lifting a pillow off the monitors. An interesting thing... according to all the metering we were doing, both sides of the preamp were pushing the meters to the same levels, but the SOUND from the Sylvania tube was noticeably louder, had better highs and lows and the mids were not so muddy. Needless to say, I swapped out both the Edicors and dropped in the Sylvania tubes.

Then we compared the TL Audio after the NOS tubes were dropped into it with a Summit Audio 2BA-221. They compared very similarly after the tube upgrades. I was pleasantly surprised. The D.I. on the Summit sounded better, but not by much. The mic pre side of the comparisons were different, not better, than each other.

I mention all this in this forum because I see these older TL Audio pres selling for pretty low prices. I humbly suggest they are worth picking up if you then drop better tubes into the box. It is totally easy to do.

Another thing worth mentioning regarding the TL Audio Dual Valve mic pre is the interior of the box is HUGE. There is a lot of space in there. It is a two rack space unit. Some might say there is a lot of wasted space. But I am looking at it with the idea of adding input transformers to each channel. There is plenty of room for this mod inside the box. Sweet! I plan to place toggle switches on the front panel of the preamp to switch the trannies in or out of the signal, thus getting another sound out of the preamp. That is, when I get some more $$$ to buy the transformers.
Puffer did you ever do the transformer mod?
Old 23rd April 2012
  #33
Yes, I did! I actually had my very capable, creative friends at Full Custom Repair in Lemoyne, PA do the work for me. I made a thread documenting the effort... it's someplace around here. If you are interested, a search should make it pop up pretty fast... TL Audio PA-2 mods or something like that would get you there.

I picked up a pair of used Beyerdynamic mic input transformers. I do really like how the signal sounds with the transformers switched in the circuit. However, how my friends at Full Custom Repair implemented the transformers into the circuit, well there is a very big drop in gain when the transformers are engaged, so that is a bummer. Still useful on loud sources like guitar amps or drums, but not quiet stuff.

I was JUST looking over the schematic for the PA-2 yet again last week. It occurred to me that the input layout looked pretty familiar.... Circuit detectives alert! I have been spending a lot of time recently messing around with some THAT1512 chips and the input circuit on the TL Audio PA-2 is pretty much the same transformerless circuit but with an older input chip than the THAT1512. Interesting. The transformerless output of the PA-2 is the same circuit as a DRV134, but with an older chip playing the driver's role. So the PA-2 is BASICALLY the same preamp as a Five Fish SC-1 with a tube slapped in the center of the circuit, or the same thing as a newer Rane MS1S, again with a tube slapped into the center of the circuit.

Hmmm..... Of course the tube is doing some good stuff to the sound. I can say with certainty that the PA-2, even with its older chip sets, has a different, but pleasing sound with the tube in there, compared to the clean THAT1512 circuit. I have both, I use both and listen to both--it's true. They both sound good, but are NOT the same.

I have been messing around with adding transformers to the THAT1512 circuit and am still working through it all. I THINK I have a better way of adding the input transformer to the PA-2 circuit than the guy who did the work for me figured out. That is not a bust or criticism on his effort, I have spent way too much time on these things at this point, much more time than my friends did and it is only natural that I would have come up with a different (and hopefully better) plan after all this time.

BTW... an OUTPUT transformer on the PA-2 is TOTALLY possible. It would be easy to add a switch to choose between the output driver or the transformer. This effort would be less expensive than an input transformer as well! If you are into that heavily saturated output transformer sort of thing, this mod would get you there. I have done it on another similar circuit and the results are pleasing... if you are into that saturated steel core transformer thing. I know I am! A 1:1 output transformer would give you a slightly lower output because the output driver provides up to 6dB of gain to the signal, but I think having the output transformer as a choice in your preamp tool kit is worth losing a little gain on the output.
Old 24th April 2012
  #34
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I have the pa-1, might be different altogether?
Old 24th April 2012
  #35
They are indeed different--the PA-1 has the tone controls and the trim control. The PA-2 only has a gain control for each channel. How different the circuits are though, I simply can not say, as I have never seen the schematic for the PA-1. Have you ever seen the schemo for the PA-1?

BTW--if you ever need information for you box, the people at TL Audio were very helpful when I gave them a call. Very prompt and helpful, the way customer service SHOULD be.
Old 26th April 2012
  #36
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Quote:
Originally Posted by Puffer Fish View Post
They are indeed different--the PA-1 has the tone controls and the trim control. The PA-2 only has a gain control for each channel. How different the circuits are though, I simply can not say, as I have never seen the schematic for the PA-1. Have you ever seen the schemo for the PA-1?

BTW--if you ever need information for you box, the people at TL Audio were very helpful when I gave them a call. Very prompt and helpful, the way customer service SHOULD be.
Thanks Puffer for your help bud.
Old 10th June 2012
  #37
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Sorry to revive this older thread....

I have a TLA indigo voice processor (with a few tubes ...).
It does make awfull hiss and some drops.

I got it second hand like 10 years ago and never changed the tubes !!!

Would the change of tubes clean all the noise or is it not related ?

F
Old 10th June 2012
  #38
Quote:
Originally Posted by flober1970 View Post
Sorry to revive this older thread....

I have a TLA indigo voice processor (with a few tubes ...).
It does make awfull hiss and some drops.

I got it second hand like 10 years ago and never changed the tubes !!!

Would the change of tubes clean all the noise or is it not related ?

F
The noise could be related. If it were me, I would replace the tubes and fire it up. Is there a repair shop nearby with folks you are friends with? If so, maybe they have some tubes that were pulled from repaired guitar amps you could try dropping into your voice processor and give it a listen. If you can't find any used tubes laying around to listen for differences in the sound, you are stuck buying new.

I am not familiar with this particular box, so I can't suggest what goes in there and how much it might cost you. These things typically take 12AX7 preamp tubes. I am pretty certain TL Audio played around with some EF86 preamp tubes as well.

My favorite new production tubes are made by JJ. A reseller of their tubes in the United States that I have had very good luck with is Eurotubes, out of Oregon. If you go to their web site you can see for yourself how much the various tubes cost. I humbly suggest you purchase the gold pin variety of their tubes if you decide to buy tubes from them for your unit. Check them out here: Eurotubes | Preamp Tubes, Retube Kits, Speakers, Damper Rings
Old 11th June 2012
  #39
Lives for gear
 

Funny this thread just came back up.. I just noticed that ch2 of mine is out - I suspect it's the 20yr old tubes... going to swap them and hoe that's all it is.
Old 11th June 2012
  #40
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thanks for the advices, unfortunatly I live in a remote place with no repair shops in the area (in Beijing, 3000km away). I believe the voice processor has 5 tubes, pre, comp, 3 stage eq ...

I should open it to have a look.

besides I have one tube in a blue pre, i might swap it to hear ... with the comp and eq off !!


F
Old 11th June 2012
  #41
Quote:
Originally Posted by flober1970 View Post
I should open it to have a look.

besides I have one tube in a blue pre, i might swap it to hear ... with the comp and eq off !!


F
Good idea. That should at least give you some insight into how the tube is affecting the signal.
Old 18th June 2012
  #42
Gear Nut
 

Couldn't resist chiming in - I picked up a 5051 for very little money and did some extensive experimenting from my cache of valves. Stock, it was kinda muddy and a little shrill/peaky in the upper mids (if you can imagine both simultaneously).

I tried (all ECC83):

- 1963 (yellow print) Blackburn Mullards: thick, 3D, crystal clear, silky top
- 60s Dutch Mullards: very thick, massive bottom, very clear, strong low mids
- ribbed Telefunkens: scooped mids in comparison to Mullards, crystal clear across whole range, more 'hi-fi', less rich
- JAN Sylvanias: great bass, more 'boxy' (i.e. more mid emphasis) than the above, very clear

I stuck with the Blackburn Mullards because they sounded the best on a broad range of material. the Sylvanias were much closer to Mullards than to the Telefunkens in sound.

Anyway, with a change of valves, the 5051 stands up to some $$$ pres that I have, albeit with very little in the lowest sub... so not so good for bass instruments. I think I'm gonna try swapping out the opamps.
Old 18th June 2012
  #43
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Peter H. Boer's Avatar
Quote:
Originally Posted by harrypurser View Post
Anyway, with a change of valves, the 5051 stands up to some $$$ pres that I have, albeit with very little in the lowest sub... so not so good for bass instruments. I think I'm gonna try swapping out the opamps.
I'm using my 5051 for bass all the time, but it was extensively modded. see TL Audio Ivory 2 5060 Valve replacement
Old 22nd June 2012
  #44
Gear Nut
 

Quote:
Originally Posted by Peter H. Boer View Post
I'm using my 5051 for bass all the time, but it was extensively modded. see TL Audio Ivory 2 5060 Valve replacement
Ah, fantastic - I'll PM you about this!
Old 10th October 2012
  #45
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mprooxis's Avatar
 

Love this thread...I have all kinds of gear and several TL Audio gray , blue and red models. I love their consistant sound and quality that stand up to some newer Neve gear i have. Havent had a problem with my tube ones. I have the dual gray mic pre with compressor, a blue indigo dual eq and a red crimson dual compressor. Because of this cool thread I think I will experiment with swapping out one side of the tube gear and compare the results with channels that have not been swapped out. As with everyone here, gear and tone and quality is a never ending quest.
Old 10th October 2012
  #46
Quote:
Originally Posted by mprooxis View Post
Because of this cool thread I think I will experiment with swapping out one side of the tube gear and compare the results with channels that have not been swapped out.
It can be a very illuminating procedure comparing tubes this way. No matter what you decide is the best sound for your needs, comparing two tubes in this manner really can show the differences between tubes---some of it is rather subtle, but some of the differences can be drastic. It is just good stuff to know when making tube choices for the future. I know you'll have a great time doing this. I certainly did!
Old 10th October 2012
  #47
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thanks for starting this thread Puffer Fish. I know you posted before which tubes you used in your swap, but just real quick, which ones were they and were did you get them?
thanks in advance for repeating your info.
Old 10th October 2012
  #48
Yikes! I am not sure I remember which tubes remained in the PA-2! I know I have tried the JJ 12AX7 long plate gold pin tubes and they are my fave new production preamp tubes.

I might have settled with a pair of Sylvania tubes in the PA-2. Interestingly enough, they are long plate tubes, similar to the JJ tubes. Or at least they seem similar to me, but I am not a tube manufacturer! They do have a similar sound which I really dig.

The JJ tubes I buy from Eurotubes out of Oregon. They are an online store and deal only with JJ tubes. Check them out: Eurotubes - Vacuum Tubes by JJ Electronic - ECC83, 12AX7, 6L6. 6L6GC, EL84, EL34, KT77, KT66, KT88 They have a bunch of different tubes. The people are very helpful. these will be cheaper than going with NOS tubes.

The Sylvania tubes I really like were indeed NOS tubes. I picked them up from some friends of mine who do guitar amp work. It was a one time deal. I cleaned out a bunch of the NOS tube stock they had and they gave me a great deal because the tubes were not selling. I will not be finding that deal again. Oh well.

I have also used mullard, RCA, GE, amperex and other NOS tubes. They all have their own sound. Some I liked better than others. But I must say, I really do like the JJ ECC803 S gold pin tubes (that's the 12AX7 long plate gold pin tube)--I like it differently than the NOS stuff I have had the opportunity to use. The JJ tubes are a better source for consistency and of course are also readily available. And the price is right!

I hope that helps.

Use the best tubes you can find. try the JJs if they seem interesting to you. I do implore you to try NOS tubes if you can get a line on them and have the $$$ to pick some up. Good luck!
Old 11th October 2012
  #49
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Very cool and thanks Puffer Fish. I'll try the JJ's first.
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