cap upgrade worth it?

[rntlee]

Hi, I've got a Chinese amp here (Yaqin) and the only caps in the signal path are the coupling caps between the PI and the power tubes. The caps they used look to be these Pilkor (Philips) caps.
Do you think a noticable improvement could be made by changing these out for a higher quality cap? The sound is actually quite good, but could an upgrade remove any residual graininess to the sound? Any recommendations? Thanks.

 

[KatieandDad]

Those film caps shouldn't be too bad.

Try bypassing them with some 1nF Polystyrene caps to see if that makes any difference.

 

[Dimitris AR]

Hi , I use the Pilkor ( Philips 378MKP series ) in my OTL PL36 amp and they sounds very good to my ears .

 

[rntlee]

Thanks guys,
I guess I'll leave well enough alone!

 

[DHT112A]

The caps in your picture are rated X2 intended more for EMI suppression and probably not the best for audio.

 

[rntlee]

Thanks for the reply,
is it worthwhile to change them in your opinion?

 

[rntlee]

X2's are also a "safety" rated cap, right? Is this necessary for a cap that's coupling stages together?

 

[lanchile]

Thanks for the reply,
is it worthwhile to change them in your opinion?

DHT112A is right! you should use the right ones for audio like:
Sonicap,Auricap,Mundorf etc

 

[rntlee]

Do you think they used X2's because they will fail open, and not shorted?

 

[astouffer]

Do you think they used X2's because they will fail open, and not shorted?

More like they were the right price.

 

[rntlee]

More like they were the right price.

Perhaps, but I think regular film caps would source cheaper than safety caps. There's no other advantage to using these?

 

[Dimitris AR]

Αs I said before I use Philips / Pilkor or BC 378 MKP series which they aren't safety caps , but in other amp I tried the X2 caps Philips and Arcotronics with good results too , so the choice is your's .

 

[rntlee]

Thanks Dimitris,
I think that sonic improvement would be pretty minimal vs. cost, so I'm going to leave them be. Plus they have the added benefit of protecting the grid of the El34's in the event that they should fail!

 

[Dimitris AR]

Thanks Dimitris,
I think that sonic improvement would be pretty minimal vs. cost, so I'm going to leave them be. Plus they have the added benefit of protecting the grid of the El34's in the event that they should fail!

Hi rntlee , it would be better to make some improvements in the circuit of the amp , if you want I will try to help you .

 

[gingertube]

These are Meatlaised Polypropylene caps.

Polyproylene Film/Foil may give a marginal improvement in performance if you have them already in your parts bin. If not, I would leave them alone.

Cheers,
Ian

 

[rntlee]

These are Meatlaised Polypropylene caps.

Polyproylene Film/Foil may give a marginal improvement in performance if you have them already in your parts bin. If not, I would leave them alone.

Cheers,
Ian

Thanks Ian,
I am going to leave them be for now.
( I know you wanted to type metalized! )

Hi rntlee , it would be better to make some improvements in the circuit of the amp , if you want I will try to help you .

I would be interested in your opinion of the circuit. I've got a schematic...it's got a couple of errors (R120 is in the wrong spot, R107 is actually R127 on the board) Here's the schematic I have:


I measured a few voltages referenced to ground and marked where R120 actually is in this partial schematic:

 

[gingertube]

Upgrades?

If you do not object to "sand" in your amp then replacing R108 and R208 with simplen current sources (3.6mA) as shown in the attachment sould give a worthwhile improvement.
Cheers,
Ian

 

[Dimitris AR]

Hi Ian , the curent of the two tubes V103 and V104 is 6mA not 3.6mA .

 

[gingertube]

Humm!! 345V - 225V = 119V across 68K is 1.8 mA

2 times that (for each of V103 and V104) = 3.6mA

Not sure how you came up with 6mA.

If you make this change (adding the current source) it will also be necessary to change the anode loads to be equal, make them both 68K.

Cheers,
Ian

 

[Dimitris AR]

Modifications

Increase capacitors C106,C111, C112 to 100μF( or higher ), make R119 and R120 -10ΚΩ 5W and R109, R129 - 33KΩ 2W , and you can remove the two capacitors ( as shown in the schematic ) C101 220μF , this will decrease the gain but the amb will sound more cleaner due to the lack of any electrolytic caps in the signal path .