UGS - Muse edition

[Ine]

Hi,
just wondering..... Why do I have 1.6dB loss in my buffer-module ? Should it not be 1/1 ? I am using dualfets, group BL. Have also tried group GR, same result.
UGS-modules: Originally the feedback resistor (Rfb) is 56K. I am using dualfets, group BL. I have to increase this resistor to 68K to have 4.5dB gain in the UGS-module.
So...,to compensate for the loss in the buffer-stage (1.6dB), I have to increase the gain in the UGS-module, and increase the feedback resistor (Rfb) from 56K to 82K to obtain 4.5 dB unbalanced output.
HELP !

Johnny

Google translate:






Salut,
Je me demandais simplement ... Pourquoi ai-je une perte de 1,6 dB dans mon module-tampon? Ne devrait-il pas être 1/1? J'utilise dualfets, groupe BL. Ont également essayé le groupe GR, même résultat. :cri:
UGS-modules: à l'origine, la résistance de rétroaction (Rfb) est de 56K. J'utilise dualfets, groupe BL. Je dois augmenter cette résistance à 68 Ko pour avoir un gain de 4,5 dB dans le module UGS.
Ainsi ..., pour compenser la perte dans le buffer-stage (1.6dB), je dois augmenter le gain dans le module UGS et augmenter la résistance de rétroaction (Rfb) de 56K à 82K pour obtenir une sortie asymétrique de 4,5 dB .
AIDEZ-MOI !

Johnny

[patroussea]

Bonjour Ine
regarde tes MP, je t'es transféré le fichier l'UGS pour les nuls, tout y es expliqué (mais en français).

personnellement j'ai du mal à comprendre ce qui t'arrive, mais je n'ai pas fait assez de mesures sur le mien peut-être pour voire ce problème ?

bonne chance.

tiens nous informé de tes avancées et problèmes.

Pat

[patroussea]

Je vous avais rapporté il y a qq temps que je ne pouvais plus utiliser le bouton du volume, je faisais tout avec la téléco, et bien ma fille a trouvé la solution. On appuit sur le mute, pas le on/off long, et après un second appuit court le réglage du volume revient actif.

fonctionne 5h/jour chez moi, pratiquement jamais arrêté depuis la mise sous tension. Toujours aussi exellent.

[patroussea]

Quelqu'un pourrait me dire si la fonction balance fonctionne des deux côtés chez lui ?

merci

Pat

[Alex_twn]

Hi,
just wondering..... Why do I have 1.6dB loss in my buffer-module ? Should it not be 1/1 ? I am using dualfets, group BL. Have also tried group GR, same result.
UGS-modules: Originally the feedback resistor (Rfb) is 56K. I am using dualfets, group BL. I have to increase this resistor to 68K to have 4.5dB gain in the UGS-module.
So...,to compensate for the loss in the buffer-stage (1.6dB), I have to increase the gain in the UGS-module, and increase the feedback resistor (Rfb) from 56K to 82K to obtain 4.5 dB unbalanced output.
HELP !

Johnny

Google translate:






Salut,
Je me demandais simplement ... Pourquoi ai-je une perte de 1,6 dB dans mon module-tampon? Ne devrait-il pas être 1/1? J'utilise dualfets, groupe BL. Ont également essayé le groupe GR, même résultat. :cri:
UGS-modules: à l'origine, la résistance de rétroaction (Rfb) est de 56K. J'utilise dualfets, groupe BL. Je dois augmenter cette résistance à 68 Ko pour avoir un gain de 4,5 dB dans le module UGS.
Ainsi ..., pour compenser la perte dans le buffer-stage (1.6dB), je dois augmenter le gain dans le module UGS et augmenter la résistance de rétroaction (Rfb) de 56K à 82K pour obtenir une sortie asymétrique de 4,5 dB .
AIDEZ-MOI !

Johnny

Hi Johnny,

Yes the buffer should have a unity gain.
What you observe here is strange...
Did you try removing the modules and testing them individually, just powering them and measuring Vout / Vin?

Quelqu'un pourrait me dire si la fonction balance fonctionne des deux côtés chez lui ?

merci

Pat

Salut Pat,

Pas de pb chez moi, la balance marche parfaitement des 2 cotes.

[Ine]

Hi Alex

[quote]Hi Johnny,

Yes the buffer should have a unity gain.
What you observe here is strange...
Did you try removing the modules and testing them individually, just powering them and measuring Vout / Vin?[quote]

No, I have not tried that, but I will do.
Johnny

[Alex_twn]

Hi Johnny,

I just realized one thing. Try first with both output selected and let me know if you still lose 1.6dB.

[Ine]

Hi Johnny,

I just realized one thing. Try first with both output selected and let me know if you still lose 1.6dB.

Hi Alex
You just realized a very significant thing. When both output enabled, the missing gain was found. The output signal increased with 0.52V Pk-Pk . That would be an increase equal to 1.26dB ! I will change the feedback resistor in UGS from 82K , back to 68K tomorrow, because I now have a total gain of 5.66dB (with Rfb = 82K) ! Will do some more measurements after the change of the Rfb resistors . Will report the results here.
Can you please explain why the differences ?
Thanks
Johnny

[Alex_twn]

Hi Johnny,

I just realized looking again at the schematics that the R value I put across the output relay is really too low and impact the input impedance of the following stage when having a dual output.

I explain myself, I added this resistor on the very first prototype to avoid clic / plops in the speakers when muting the preamp, because the input of amp will be floating exactly when the relay is commuting. This was working perfectly with one output only as the prototype was.
Then moving to the final version with dual output, this R becomes a problem then as when using one output only, the other one is always muted and then the R becomes in parallel with the following input impedance. Not good with 1K ...!
Not surprising that the level is dropping...
Just replace it with a much larger value.

I personally use dual output always so ever realized this before. Thanks for finding this !

[patroussea]

J'avais déjà remarqué ce problème, et listé dans mes listes de remarques aux début de mes tests, mais pas les autres visiblement.

quelle serait la solution alors ?

merci

Pat

[Alex_twn]

Ben augmenter la valeur des R comme écrit ci-dessus.

[Ine]

Hi Johnny,

I just realized looking again at the schematics that the R value I put across the output relay is really too low and impact the input impedance of the following stage when having a dual output.

I explain myself, I added this resistor on the very first prototype to avoid clic / plops in the speakers when muting the preamp, because the input of amp will be floating exactly when the relay is commuting. This was working perfectly with one output only as the prototype was.
Then moving to the final version with dual output, this R becomes a problem then as when using one output only, the other one is always muted and then the R becomes in parallel with the following input impedance. Not good with 1K ...!
Not surprising that the level is dropping...
Just replace it with a much larger value.

I personally use dual output always so ever realized this before. Thanks for finding this !

Hi Alex
Changing the resistors value....is a pain in the .......Don't really want to do this, it means a lot of work ! But, if I understand this right, it is just to enable both outputs in the menu, and just use one of them ?
I have done this in menu, and it measures o.k now. No loss in the buffers. Will the output impedance be right now ?

Cheers
Johnny

[Alex_twn]

Hi Johnny,
Right these resistors are not easy to replace, I agree...
So yes just always use dual output as I am doing and everything will be fine.
I personally think that this dual output feature has a very limited interest so not a big deal.

[patroussea]

donc on remplace R29, R30, R31 et R32 qui faisaient 1K par quel valeur ? 10K ? 100K ?

merci

[Alex_twn]

10K me semble trop faible vu l'impedance qui suit. Il faut que cela soit largement supérieur pour ne pas avoir d'effet indésirables.
Tu peux essayer 100K.