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I am thinking of building a passive transformer preamp as seen in AudioXpress, Jan 05. I will use it as volume control and to step up the gain betweena Sony 777ES CDP / Audionote DAC an Cary SLM 70
monoblock amps. Does any one have a opinion on the subjective sonics between the passive preamp and a tubed based preamp. The passive preamp is cheeper to build and is a very simple layout.Thanks
Tom R.
Follow Ups:
a new preamp that 'should' be available very, very soon from SMc Audio. That would be Steve McCormack's outfit.It's a passive with buffer, and it simply is the most transparent, dynamic, resolute preamp I've heard, passive or active. I have owned/extensively auditioned the likes of EVS ultimate attenuators, resistor-based passive box, Bent TVC, multi $$$$ active SS/tube preamps, and this one from SMc audio will simply be the ONE. And it should come in at a moderate price, as heard through the grapevine..
I haven't had much luck finding alts for my mk ii tvc.Is the new unit similiar to the older tlc? I think that was a buffer passive also.
Believe what your ears say - not hearsay.
Never heard a TLC before, but people have reported that TVC's, etc, are better than TLC.The new preamp is a "buffered passive" like TLC was, but you must realize this new pre will be the culmination of many years of development by Steve, way after TLC has come out. No, I don't believe TLC and the new pre will be in the similar ballpark at all, and I suspect Steve will say the same thing. I just hope he gets to the market ASAP.
a new preamp that 'should' be available very, very soon from SMc Audio. That would be Steve McCormack's outfit.It's a passive with buffer, and it simply is the most transparent, dynamic, resolute preamp I've heard, passive or active. I have owned/extensively auditioned the likes of EVS ultimate attenuators, resistor-based passive box, Bent TVC, multi $$$$ active SS/tube preamps, and this one from SMc audio will simply be the ONE. And it should come in at a moderate price, as heard through the grapevine..
Does this unit have voltage gain or is it just a 1:1 transformer with a buffer?
se
If I remember what Steve said, it is an attempt to have the best of passive and active designs. Something like, transformer-coupled phase-splitter--> shunt-type resistor volume control--> Fet buffer stage.I understand he's finalizing chassis material/design at this point..
If I remember what Steve said, it is an attempt to have the best of passive and active designs. Something like, transformer-coupled phase-splitter--> shunt-type resistor volume control--> Fet buffer stage.
Ah, ok. I started down that path about 15 years ago with the AL-1, which Corey Greenberg based his Aunt Corey's Buffered Passive Preamp on. Though the AL-1 didn't use an input transformer and the output was an integrated circuit buffer (a PMI BUF-03).
It's evolved a bit since then with the addition of an input transformer and a switch from an IC output buffer to a discrete one. The current version uses a single-ended hybrid tube/bipolar follower.
It's currently driving a little flea-powered amp that uses the same basic topology but with a 1:8 step-up transformer for fully passive voltage gain.
Anyway, glad to see that this basic approach has worked well for others. It's worked quite well for me over the years.
se
Hi Steve,I am interested in knowing what you think are the functions served by the input transformer (I assume it is 1:1) besides the effect of separating the grounds of the source and the load, and why in your view they improve the sound quality enough to outweigh the common technical issues associated with a transformer.
By the way, I have three 1:1 output transformers from CineMag, following the recommendation you made in a post here a while back. I got them mainly for the purpose of converting non-single-ended outputs (e.g., the outputs from a digital amp) into single-ended signals. I wanted high-quality transformers with a good frequency response in the bass, since the intended application was to derive the bass signals in a biamping setup. I may just try adding those CineMag transformers to a BUF-03 buffered passive pre I made to see how the sound changes.
Best,
Kurt
I am interested in knowing what you think are the functions served by the input transformer (I assume it is 1:1) besides the effect of separating the grounds of the source and the load, and why in your view they improve the sound quality enough to outweigh the common technical issues associated with a transformer.
Well, they also have outstanding common-mode rejection, better than most any electronically balanced input and maintain that outstanding common-mode rejection (about 100dB at 60 Hz) even when fed from an unbalanced, single-ended source.
Beyond the technical, I really don't know exactly why the addition of the transformers sounded better to me than without. It may well be due to watever imperfections exist in the transformer rather than in spite of them. If that's the case then so be it. My goal at the end of the day is the most pleasurable experience when listening to reproduced music, not trying to achieve objective perfection.
By the way, I have three 1:1 output transformers from CineMag, following the recommendation you made in a post here a while back. I got them mainly for the purpose of converting non-single-ended outputs (e.g., the outputs from a digital amp) into single-ended signals. I wanted high-quality transformers with a good frequency response in the bass, since the intended application was to derive the bass signals in a biamping setup.
Great! I hope you found the folks at CineMag as much a pleasure to deal with as I did.
I may just try adding those CineMag transformers to a BUF-03 buffered passive pre I made to see how the sound changes.
Well that's certainly the best way to find out if YOU'LL like it or not. :)
What are you using for volume control?
se
Hi Steve,Thanks for the response. I've read about several cases (inlcuding yours) in which the addition of a transformer in the signal chain appears to make the sound more pleasant to listen to, and I find it intriguing.
The people at CineMag are indeed very nice to deal with.
I used to use only resistor-based stepped attenuators for volume control, and did not find any active pre, including the so-called buffered passive, that sounded as clean as the simple attenuators. Neverthelesss, recently I started using those cheap Panasonic and JVC digital receivers to biamp my main system and other projects and to drive a multi-channel system for SACD playback. This eliminates the need for any preamp or separate volume control. Perhaps I'm getting lazy, but it is nice to be able to control the volume using a remote control, and the digital amps really do not sound too bad.
Best,
Kurt
Hi,Ignoring for now Mr. Elliano's design (as it has well known drawbacks) you can get a number of different Transformer based volume controls from a number of sources. The ones I have liked best among those I have tried so far come from Stevens & Billington, other sources such as Sowter, Audio Consulting and even a number of inexpensive chinese products exist.
If you google for the terms "TVC" or "Transformer Volume Control" you will find quite a number of references with a lot of good info.
I personally have not yet found an active linestage that is the equal of my S&B TX-102 equipped MF Audio Passive Preamp, but cost is quite high. I'd list the linestage from Arthur Loesch's Preamp a close second and I also very much like what I term "Euridice Utimado" - or "The ultimate Euridice".
But that active preamp has a silver transformer volume control from S&B as input AND a (ideally silver) S&B Line Output transformer making it quite an expensive proposition and not really better than the straight TVC and also needs a complex and expensive PSU. But the friend of mine who uses does need the low output impedance ( < < 100R) AND the gain (20db) the Euridice offers for his active, multiamped setup....
Ciao T
If so I am curious of your opinions. And if not can you comment on technical grounds?
Russ
Hi,Fundamentally speaking, an autoformer is just a transformer where primary and secondary are actually the same. They are subject to the same sort of issues than transformers.
Though some people have observed that running the S&B TX-102 MKII in autoformer mode sounds a lot better than using it as full TVC (I hope they have not forgotten to wire the primary in parallel with the secondary though, as failure to do so will create all sort of funniness and resonances), when I did the same test with a MKI I felt that there was little to choose. I have not tried again with my MKIII's, sorry.
So, in the end I somewhat think the issue of full transformer vs. autoformer is largely moot, the main benefit from Autoformers over full transformers is in the manufacturing, eg Autoformaer is cheaper to make, but depending on quality not by much.
Ciao T
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Does any one have a opinion on the subjective sonics between the passive preamp and a tubed based preamp. The passive preamp is cheeper to build and is a very simple layout.
Your AudioNote DAC may not get along too well with that solution.
Unfortunately it wasn't mentioned in the AudioXpress article, but that passive preamp design has a punishingly low input impedance of around 150 ohms. Something a lot of tube output stages would choke on.
Also that design wants to be driven by a source impedance no greater than 150 ohms. Do you know what the output impednace of your AudioNote DAC is?
se
I am not sure of the DAC's output impedance, I am using a 6N1P
grounded cathode (150 Ohm to ground) output section with a Audio Note output transformer . I never measured the output impedance but
I believe it to be low? I dont have the equipment to check.
any thoughts?
I am not sure of the DAC's output impedance, I am using a 6N1P
grounded cathode (150 Ohm to ground) output section with a Audio Note output transformer . I never measured the output impedance but
I believe it to be low? I dont have the equipment to check.
any thoughts?
Instead of trying to second guess, I'd recommend EMailing Peter Qvortrup and see if he can give you the answer.
In the meantime I'd have to ask, do you really need all that voltage gain? I can't seem to find the input sensitivity spec for the SLM-70s, but I'm thinking it's probably sufficient enough that both your Sony and your AudioNote DAC would be able to drive them into clipping which means that the 20dB (give or take) of voltage gain from the PVA transformers would be overkill in the extreme.
se
You may be correct, as I am just getting educated in this area.
I have no experence with matching components, inpedance values,
dampening, etc. Almost sound like I could use a stepped atinuator
between the DAC and Amp. Do you have experience in this area?Thanks
Tom R.
You may be correct, as I am just getting educated in this area.
I have no experence with matching components, inpedance values,
dampening, etc. Almost sound like I could use a stepped atinuator
between the DAC and Amp. Do you have experience in this area?
Well yeah, but my tastes and preferences may not be quite the same as yours.
Something you may want to try is a simple passive pre using a pair of the PEC hot molded carbon pots. If you don't mind separate left and right volume controls, you can get them for about $10 each from Digi-Key.
I've had good results with these and for some they've even bested some nice stepped attenuators.
se
What resistance would you suggest? The catalog shows ranges from 100 Ohm to 5 meg @ 1/2 Watt, style RV6 in the PEC brand carbon Pots?Tom
10k would be a good compromise. Provides a sufficiently high load impedance to the source components while not having an outrageously high output impedance.Keep the passive unit as close as possible to the amp, using the shortest cable you've got.
se
I have used an Audionote DAC 1.1 with my TVC and had no problems whatsoever. Sounded great.
Oz
I have used an Audionote DAC 1.1 with my TVC and had no problems whatsoever. Sounded great.
But you're not using the ElectraPrint PVA transformer are you? I don't know what you're using (your system list just says a custom preamp designed by Kevin at K&K) but I doubt it has a 150 ohm input impedance. And that's what I was referring to when I was asking about the AudioNote DAC. Not just TVCs in general, all of which that I'm aware of have input impedances far higher than 150 ohms.
se
I only know of 2 other transformer option for passive volume control.one is here> > > > > > http://www.audio-consulting.ch/
the other below(there is a DIY kit).I've heard the ultimate attenuators and they are really good but the transformers are suppose to be better.They are very expensive though.Could you scan me the audioxpress article?I would really like to read it and possibly do .I'm using a Sony scd777es with transformer output to by pass the audio board output stage.A totallyno brainer.Mike
I only know of 2 other transformer option for passive volume control.one is here> > > > > > http://www.audio-consulting.ch/
the other below(there is a DIY kit).I've heard the ultimate attenuators and they are really good but the transformers are suppose to be better.They are very expensive though.Could you scan me the audioxpress article?I would really like to read it and possibly do .I'm using a Sony scd777es with transformer output to by pass the audio board output stage.A totallyno brainer.
It's not the same as the Audio Consulting kit.
It uses a 1:8 step-up transformer for voltage gain and a 10k potentiometer across its secondary for volume control.
It was designed by Jack Elliano of ElectraPrint and uses their PVA transformers.
Its main drawback is the exceedingly low input impedance that it presents to the source component, on the order of 150 ohms. Something which was not mentioned in the AudioXpress article.
se
Then I'll stick to the Audio Consulting DIY kits.Mike
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