Hybrid Class-D

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi John,

You are partly wrong about the input. When driven differentially the input is fully symmetrical with a Zin of 3,6k. But driven separately/unbalanced - is 1,8k and -is 10k.

Also there is something wrong with the linked file, have tried to download and open it in two different computers with no luck!
 
UcD

Dear Lars

We discussed that differential input with the designer of the UcD's, Bruno Potzeys. And we also meaured those impedances by ourselves.

Those impedances are NOT a problem when driven from a relatively low source impedance of, say <10 Ohm (such as op amps).

With the SRPP the output impedance is around 1,5 kOhm but, as found by Jacco Dekkers, the distortion from the SRPP has a relationship with the load impedance giving (in our configuration!) the best result with a load of around 3 kOhm. So we combined the input impedance of the UcD with resistors to get the best results (lowest distortion). And I must say it works fine.

Quite a number of these kits have been built by amateurs (and technicians) and all stated that it performs with the "character" of a very good tube amp combined with a very low output impedance.

John
 
John,

I also discussed this with Bruno as we are thinking of producing a hybrid but with a completely different(and truly differential:cool: ) topology than this.

He confirmed 3,6k Zin when driven diffferential.

When you measure the impedances separately they are different (1,8k/10k) but when you measure from+ to - it will still be 3,6k.

In the drive you use they will of course be different.

I also believe in that the concept with tube driver will be nicesounding.
 
John, i followed your and Jacco's project. But i think Lars is right about the 2x 1k8 impedance ( 3K6 ). You know i do not like measurements but i use the balanced input now for 2 years with 2 SRPP identical tubestages optimized for 1k8 impedance driving unbuffered Hypex UCD180st. And i can not hear distortion at high levels, so it must better then 0.5 %. My latest project with a unbalanced tube driven UCD400oem works also great.

Saturday my hybrid designs will be object for testing and listening at the "Roehren und Hoeren" meeting in Germany. I will see what the germans think of the design.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.