Importance of 500pf bypass cap on V1B

[Audiodog]

So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Skyline. All measured within 1% of each other. All three caps sounded very different. It even effected the lows. I settled on the NOS Centralab 500pf as best.

I think this position is crucial to the amp tone. Most probably don’t swap caps here. It was quite noticeable and worthy of some testing. Anyone with any experience trying different brands here?

[Audiodog]

This.

[ijedouglas]

So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Skyline. All measured within 1% of each other. All three caps sounded very different. It even effected the lows. I settled on the NOS Centralab 500pf as best.

I think this position is crucial to the amp tone. Most probably don’t swap caps here. It was quite noticeable and worthy of some testing. Anyone with any experience trying different brands here?

I have tried the new Vishay Ceramite x5f and didn't care too much for them. I found some NOS x5F sprague (shiny ala 124) and older dull. I really like both. The dull have a softer feel to them but both add great sing to the amp. When I was messing around with them I found that its critical to measure and make sure they are at least 500pf. Lower and you start to lose the sing. Ill see if I can find some centralab to test.

Did you mean to say V1b?

[talbany]

I've tried the Circle D's the Centralabs and the new XF5's and a few others ..Years back I picked up a few NOS Sprague CMO6FD's (large Mica's) Being mostly a Single coil player gives me a little more clarity on the top end especially the clean channel, I always gravitate back to them. However, at the same time do like the fatter more aggressive mids from the Centralabs especially in overdrive. The Circle D's were a little dull.(I do have some old XF5's someone sent I want to try there on my next build). This is the only spot I will use a mica.

Either way I agree there is a difference and recommend pairing it with different resistor types as well and is a great spot to tweak and balance your sound.

Tony

[Audiodog]

Only 3 of 10 measured good. The others were low. I would get the 510pf. To make sure they are big enough.

So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Skyline. All measured within 1% of each other. All three caps sounded very different. It even effected the lows. I settled on the NOS Centralab 500pf as best.

I think this position is crucial to the amp tone. Most probably don’t swap caps here. It was quite noticeable and worthy of some testing. Anyone with any experience trying different brands here?

I have tried the new Vishay Ceramite x5f and didn't care too much for them. I found some NOS x5F sprague (shiny ala 124) and older dull. I really like both. The dull have a softer feel to them but both add great sing to the amp. When I was messing around with them I found that its critical to measure and make sure they are at least 500pf. Lower and you start to lose the sing. Ill see if I can find some centralab to test.

Did you mean to say V1b?

[ijedouglas]

Only 3 of 10 measured good. The others were low. I would get the 510pf. To make sure they are big enough.

Got some on the way

Have you tried the Sprague X5F (NOS Shiny ala 124) in that position?

[erwin_ve]

Only 3 of 10 measured good. The others were low. I would get the 510pf. To make sure they are big enough.

So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Skyline. All measured within 1% of each other. All three caps sounded very different. It even effected the lows. I settled on the NOS Centralab 500pf as best.

I think this position is crucial to the amp tone. Most probably don’t swap caps here. It was quite noticeable and worthy of some testing. Anyone with any experience trying different brands here?

I have tried the new Vishay Ceramite x5f and didn't care too much for them. I found some NOS x5F sprague (shiny ala 124) and older dull. I really like both. The dull have a softer feel to them but both add great sing to the amp. When I was messing around with them I found that its critical to measure and make sure they are at least 500pf. Lower and you start to lose the sing. Ill see if I can find some centralab to test.

Did you mean to say V1b?

Or double a 270pF...

[erwin_ve]

So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Skyline. All measured within 1% of each other. All three caps sounded very different. It even effected the lows. I settled on the NOS Centralab 500pf as best.

I think this position is crucial to the amp tone. Most probably don’t swap caps here. It was quite noticeable and worthy of some testing. Anyone with any experience trying different brands here?

I have tried the new Vishay Ceramite x5f and didn't care too much for them. I found some NOS x5F sprague (shiny ala 124) and older dull. I really like both. The dull have a softer feel to them but both add great sing to the amp. When I was messing around with them I found that its critical to measure and make sure they are at least 500pf. Lower and you start to lose the sing. Ill see if I can find some centralab to test.

Did you mean to say V1b?

Vishay Ceramite have 2 types, on specsheet they are the same, but they are different one is produced in Asia, the other in Chech.

[ijedouglas]

Vishay Ceramite have 2 types, on specsheet they are the same, but they are different one is produced in Asia, the other in Chech.

Just got the ones from Mouser. Do they sound the same and how do you identify them?

[erwin_ve]

Vishay Ceramite have 2 types, on specsheet they are the same, but they are different one is produced in Asia, the other in Chech.

Just got the ones from Mouser. Do they sound the same and how do you identify them?

The yellow one on the right is vishay Ceramite produced in Asia, other orange ones are Czech produced.
They do not sound the same. I like the orange ones better, smoother in top.

[talbany]

how do you identify them?

It says it on the package (Erwin beat me to it )

20210526_114023.jpg

The Ceramite's are in my Bluesmaster. They are smooth but do not have the same low mid sound as the older X5F's do? a little thinner IMO

[ijedouglas]

Yup, I have the orange ones from Mouser.

Here are the spragues I use:

PXL_20210526_160303308.jpg

[Richard1001]

I now the type of cap can make a difference, but what i don't get is if the value is so important, why use a ceramic cap in a tube amp and close to the preamp tube? Ceramic caps drop in value drastic with only moderate temperature rise. Even holding the cap between you fingers results in a change. So what is exactly 500pf?

[ijedouglas]

I now the type of cap can make a difference, but what i don't get is if the value is so important, why use a ceramic cap in a tube amp and close to the preamp tube? Ceramic caps drop in value drastic with only moderate temperature rise. Even holding the cap between you fingers results in a change. So what is exactly 500pf?

Not sure but Mr D sure liked them I normally test a bunch with my capacitance meter (YF-150) and pick ones closet to the required value

[jcsifu]

When I was messing around with them I found that its critical to measure and make sure they are at least 500pf. Lower and you start to lose the sing.

If a higher value produces better sing, I wonder what would be the highest value that could be substituted without it being too big of a departure from the Dumble sound. Would this be something that could be switchable? Would the switch have the full 200-ish volts on it?