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Transformer coupled vs Capacitor coupled?

Guys,

I’m sure their are different schools of thoughts on these typologies but are transformer coupled better in terms of sound quality in regard to pre-amps.

Thanks,
Wig
128x128wig
georgehifi's avatar
georgehifi
10,312 posts
 
Tim de Paravicini uses transformers on the balanced/XLR inputs and outputs of his EAR-Yoshino 868 and 912 pre-amps, but of course not on the RCA’s.
I’m not 100% sure (please correct me) but I was told once, that was just to get xlr input and an output connections, but everything inside in the active tube circuit is SE (single ended) in between those input and output transformers.

Cheers George
bdp24's avatar
bdp24
9,412 posts
 

That is correct George. The EAR-Yoshino circuits themselves are single-ended, the transformers are just to provide balanced connections, as is standard in recording studios, where Tim does a lot of work (Roger Waters’/Pink Floyd’s studio in England being one such).

Roger Modjeski provides a balanced input (only) on his Music Reference RM-200 amplifier, but he told me he did that with discrete components, not transformers. The RM-200 is also a single-ended circuit.

Ralph Karsten’s Atma-Sphere designs are true dual-differential balanced circuits, as far as I know unique amongst currently-available tube amps and pre-amps.

I believe it is Ralph’s contention that balanced circuits themselves provide benefits over single-ended, Tim and Roger that balanced transmission is what they find of significant value, not the circuit itself. About that I may be mistaken ;-) --- Eric.

atmasphere's avatar
atmasphere
11,575 posts
 
I believe it is Ralph’s contention that balanced circuits themselves provide benefits over single-ended, Tim and Roger that balanced transmission is what they find of significant value, not the circuit itself. About that I may be mistaken ;-) --- Eric.
I doubt that either Roger or Tim would deny the benefits of balanced differential circuits- in a nutshell, rejection of power supply noise and also rejection of noise induced in the interconnect cables.
A secondary benefit is lower distortion as even ordered harmonics are cancelled with each succeeding stage. This means that the primary distortion product is the 3rd harmonic, which is treated by the ear in a similar manner to the 2nd (contributes to 'warmth' and 'bloom') but its level is at about 1/10th of a circuit that has the 2nd harmonic as its primary distortion component. So distortion components are not compounded from stage to stage as the signal progresses through the signal chain- this results in less coloration.
bigkidz
3,312 posts
 
Basically it comes down to implementation of the design.  All of the designs have their benefits and detriments.  Coupling capacitors have a wide bandwidth but can give up dynamics, details, and transparency to transformer coupled.  With transformer coupled you can get fantastic sound at 20K but designs up to 40K is even better.  They look pretty bad looking at the square wave but you do not need 100 to 200hz to make them sound fantastic.  I have built both (and own both) and the transformer coupled just has more transparency and details.  I use V-Capacitors in the preamplifier as I prefer their sound to the others we have tried.  The Servo design also depends on the implementation.  I have heard some that sounded very poorly but the old Luxman power amp that I have is just incredible.

So is one better sounding than than the other - to me again design implementation is the key but each has its benefits if done well.  Coupling caps is a much easier design to implement IMO.

Happy Listening.
georgehifi's avatar
georgehifi
10,312 posts
 

Sound quality
1st Direct coupled using a good dc servo (most transparent/dynamic)
2nd a Good quality Cap (large enough not to roll off the bass too early)
3rd Transformer coupled (using good transformers)

Cost to make, lowest first.
1st Direct coupled ($10-20)
2nd Cap coupled
3rd Transformer coupled.

Least distortion/coloration’s (lowest first)
1st Direct coupled (always lowest, if good design)
2nd Capacitor coupled
3rd Transformer coupled

Lowest output impedance (good to drive next piece of equipment)
1st Direct coupled (lowest from DC to wherever)
2nd Capacitor coupled
3rd Transformer coupled.


No-brainer, direct coupled wins out, cap comes in second.

Cheers George
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