Transformer Coupled Outputs

Jazzhead · May 4, 2013

This is with regard to my pre-amp , the WAVAC PRT-1 . The scant information around, tells me that it employs transformer coupled outputs. It seems that only the XLR outputs are coupled in this manner . Could those you technically more inclined , please enlighten me on the merits and shortfalls of such a coupled output and on the purpose of such an implementation . I am at present running it thru it's balanced outs , driving a Vitus SS-101 MK2 , it seems quite the match , with no perceived loss of dynamics or rolled off top end . Look forward to your thoughts.

cjfrbw · May 4, 2013

Transformer coupling at the output of a preamplifier gives a flatter impedance output over the audio frequency band. It seems to be a myth from old tube amplifiers that transformers result in rolloff or lack of detail, good ones don't.

There are also audio cult mythologoes about transformers and their esoteric qualities in regards to using them as coupling devices rather than plain resistance/capacitor networks.

Wavac uses the highly regarded Tango custom made (or they used to before Tango went out of business).

My own (probably worthless, mystical) thought is that there is some characteristic about the way transformers store and release energy that gives music a pulse and warm life, as opposed to transmitting audio as a kind of moving but less life like sculpture. However, horses for courses, lots of different opinions. I like transformer coupled audio components.

Jazzhead · May 4, 2013

The Zanden 3000 pre-am[p is another that employs transformer coupled outputs . Though here all the outputs (Single Ended & Balanced) are coupled , whereas in the WAVAC it is only the XLR outs that are coupled(wonder why?) . Both the mentioned pre-amp's are designs which were conceived a decade back if not more . Seems this practise is not as common place in today's circuit designs . Did read someplace that it does help provide better drive characteristics . I'll buy that, the WAVAC sounds incredibly dynamic and alive .

jfrech · May 4, 2013

Hi, I have 2 transformer coupled output preamps in my system right now. My Nagra PLL that I own and a Robert Koda K10 that I am demo'ing. I do think both only use the transformers on the balanced outs. The Koda K10 also has transformer coupling on the XLR's inputs. I have never heard my dCS Scarlatti sound so real an natural as I do via the Koda K10 XLR in's and outs.

I am also using a Step up Transformer (SUT - EAR MC4) off my tonearm before my phono stage. I feel I get more dynamics, more natural (seemingly anyway) warmth with no loss in resolution.a

Pretty sure the Jeff Rowland and Allnic preamps are transformer coupled also. So a interesting mix of tube and solid state designs here all employing this technology.

I am using Ayre MXR's as amps.

egidius · May 4, 2013

..vs ZOTL?

Jazzhead said:
The Zanden 3000 pre-am[p is another that employs transformer coupled outputs . Though here all the outputs (Single Ended & Balanced) are coupled , whereas in the WAVAC it is only the XLR outs that are coupled(wonder why?) . Both the mentioned pre-amp's are designs which were conceived a decade back if not more . Seems this practise is not as common place in today's circuit designs . Did read someplace that it does help provide better drive characteristics . I'll buy that, the WAVAC sounds incredibly dynamic and alive .

I am intrigued; where does my ZOTL pre by David Berning fit in these thoughts, an incredibly clean and elegant sounding unit.
??

Jazzhead · May 4, 2013

jfrech said:
Hi, I have 2 transformer coupled output preamps in my system right now. My Nagra PLL that I own and a Robert Koda K10 that I am demo'ing. I do think both only use the transformers on the balanced outs. The Koda K10 also has transformer coupling on the XLR's inputs. I have never heard my dCS Scarlatti sound so real an natural as I do via the Koda K10 XLR in's and outs.

Looks like the Koda is here to stay .. I guess you must be waiting , on how it sounds with your Altair before committing . Eagerly look forward to your thoughts

Purity Audio Design 1 · May 4, 2013

Transformer coupling is the way to go in my opinion. Not that it is a "necessity" for a good design though. We have been using transformer coupling at both inputs and outputs on all but one of our preamps since the beginning and also have our circuit configured for transformer coupling on the single ended connections as well. When doing this, ther eare other consideration that must be taken into account such as the grounding technique for the single ended RCA outputs. Be careful that they are not shorting pins 1 and 3 on the XLRs all the time as this means you do not have a true balanced output.

I feel transformer coupling adds a better sense of transparency and resolution when done properly.
Another aspect you have to look out for is the phase. The manual for any given preamp should indicate if the circuit inverts phase or not. If equipped with a phase switch, this is not much of a concern. If the unit does invert phase and no way to switch it, you have to reverse the phase at your speakers depending on the amplifier used. In a nutshell, you have to figure out where things are at when it leaves the amplifier.

Jazzhead · May 4, 2013

egidius said:
I am intrigued; where does my ZOTL pre by David Berning fit in these thoughts, an incredibly clean and elegant sounding unit.
??

Hi , I have not heard the Berning , so cannot comment . It does have a strong following though . Maybe you could tell us how it sounds in your set-up.

Jazzhead · May 4, 2013

Purity Audio Design 1 said:
I feel transformer coupling adds a better sense of transparency and resolution when done properly.
Another aspect you have to look out for is the phase. The manual for any given preamp should indicate if the circuit inverts phase or not. If equipped with a phase switch, this is not much of a concern. If the unit does invert phase and no way to switch it, you have to reverse the phase at your speakers depending on the amplifier used. In a nutshell, you have to figure out where things are at when it leaves the amplifier.

Bill ... have heard good things about your amps, look forward to having a listen sometime soon .

jfrech · May 4, 2013

Jazzhead said:
Looks like the Koda is here to stay .. I guess you must be waiting , on how it sounds with your Altair before committing . Eagerly look forward to your thoughts

Yes, you got it. I really want to hear it with the Rockports...so I'll be replying soon to let you know. I am listening to it now still with the Maxx 3's...had my Nagra PLL back in for the last few days. The Koda K10 is cold...been jiggled around and the cables moved. But damn...it sounds beautiful. I am sure I'll regret these words soon..but If I would have heard this preamp before I heard the Rockports...I wonder...so that might be a hint to how good it is...

jfrech · May 4, 2013

Purity Audio Design 1 said:
Transformer coupling is the way to go in my opinion. Not that it is a "necessity" for a good design though. We have been using transformer coupling at both inputs and outputs on all but one of our preamps since the beginning and also have our circuit configured for transformer coupling on the single ended connections as well. When doing this, ther eare other consideration that must be taken into account such as the grounding technique for the single ended RCA outputs. Be careful that they are not shorting pins 1 and 3 on the XLRs all the time as this means you do not have a true balanced output.

I feel transformer coupling adds a better sense of transparency and resolution when done properly.
Another aspect you have to look out for is the phase. The manual for any given preamp should indicate if the circuit inverts phase or not. If equipped with a phase switch, this is not much of a concern. If the unit does invert phase and no way to switch it, you have to reverse the phase at your speakers depending on the amplifier used. In a nutshell, you have to figure out where things are at when it leaves the amplifier.

Bill I appreciate you replying here. I know some get irritated when manufacturers reply, but you seem pretty classy and just discussing your knowledge and what you have experienced. I've read great things about your preamps...

DonH50 · May 4, 2013

I am not sure why a transformer-coupled would provide flatter impedance; technically I would guess the opposite for most loads, but it is very component dependent. My guess why transformers on the pre-amp outputs is to convert the single-ended output from a cathode-follower or whatever to a balanced output for the XLR jacks. Almost all tube preamps I have seen are single-ended. That is also part of the reason a tube preamp in front of a SS amp still provides a tube "character" to a system.

IMO/IME - Don

cjfrbw · May 4, 2013

tomelex said:
this is the effect many describe of odd order harmonics being added to the signal...and thats one thing transformers do...and so do tape above say -10VU...and so does many solid state...

the other thing they do is shift phase of signals through them, and this can result in a warmer sound, or if done wrong a very irratating fatiguing sound...

as you said, they can be flat frequency response wise through the audio spectrum when used at line level, but when you pump power through them as in an output transformer distortions set in fast, especially the low end with tube drive....but, your ear is less able to discern low end distortions anyway..but intermod and stuff happens as well by the time it gets to the speakers so its a "thang" you live with, there is always compromise in electronics..

i think they are plenty good enough for pre-amps outputs or inputs to pre amps or power amps, etc.

Boy, you really know how to harsh my mystical mellow with objectivist reality.

Andre Marc · May 4, 2013

DonH50 said:
I am not sure why a transformer-coupled would provide flatter impedance; technically I would guess the opposite for most loads, but it is very component dependent. My guess why transformers on the pre-amp outputs is to convert the single-ended output from a cathode-follower or whatever to a balanced output for the XLR jacks. Almost all tube preamps I have seen are single-ended. That is also part of the reason a tube preamp in front of a SS amp still provides a tube "character" to a system.

IMO/IME - Don

??? I think there a large number of fully balanced tube preamps
on the market. I can name two dozen off the top of my head.

mep · May 4, 2013

Andre Marc said:
??? I think there a large number of fully balanced tube preamps
on the market. I can name two dozen off the top of my head.

OK, name 24 of them off the top of your head and we will see how many are truly balanced circuits vice tube preamps with XLR outputs.

DonH50 · May 4, 2013

I suppose the important part of my post is "almost all tube preamps I have seen"... I would appreciate it if you would name a few so I can update my references. I have not kept up much with tube preamps recently... The ones I have seen were Dynaco (!), Audio Research, C-J, few others, plus a bunch of guitar amps and pro sound preamps. Not in the last few years, however, so perhaps things have changed.

Andre Marc · May 4, 2013

mep said:
OK, name 24 of them off the top of your head and we will see how many are truly balanced circuits vice tube preamps with XLR outputs.

Multiple models from ARC, Atmasphere, BAT, McIntosh, Herron, Audiovalve, Aesthetix,VTL, Rogue, etc

Andre Marc · May 4, 2013

DonH50 said:
I suppose the important part of my post is "almost all tube preamps I have seen"... I would appreciate it if you would name a few so I can update my references. I have not kept up much with tube preamps recently... The ones I have seen were Dynaco (!), Audio Research, C-J, few others, plus a bunch of guitar amps and pro sound preamps. Not in the last few years, however, so perhaps things have changed.

For sure the almost all ARC models, minus the SP17, the BAT stuff, AtmaSphere,
VTL, McIntosh, not sure about CJ.

mep · May 4, 2013

Some of ARC's tube preamps are truly balanced, Atmasphere has two models, BAT certainly has more than a few models, and Aesthetix has some. VTL preamps aren't pure tube no matter what they say and I don't know about Rogue with regards to being truly balanced.

Andre Marc · May 4, 2013

mep said:
Some of ARC's tube preamps are truly balanced, Atmasphere has two models, BAT certainly has more than a few models, and Aesthetix has some. VTL preamps aren't pure tube no matter what they say and I don't know about Rogue with regards to being truly balanced.

Rogue has two fully balanced models, the Athena and Hera.

Transformer Coupled Outputs

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