hard to play amp - cure ? Clip added

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mat
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hard to play amp - cure ? Clip added

Post by mat »

Ok, now really noob question to the pros :oops:

(I'm not nesessearly talking about my new build :oops: ).
What if You end up with a build (any style amp) that seems to be a quite hard to play ? Sometimes the notes bark loud and there might be a very little sustain. If the voltages are right and wiring and lead dress has been done in a proper way. Tubes would be OK. Right component used...etc.

1. What to suspect to be wrong ?

2. What to try to improve the playability ?

Would You try to lower the voltage to the power tubes or what. (On my build I'm pushing the EL34 with 488V's right now.)

I really love the D-style amps for their accurasy and ability to reproduce slightest nyances of the playing but on the other hand every time I listen Fuch amp clips I cannot but drool for their liquidness and sustain.

My resent HRM build 'sings' very beautifully (better than my nonHRM that more likely howls :? ). The singing is not so loud than on the nonHRM and it is more easily controlable.

Anyway I would like to have little more sustain on my HRM build for it to play little easier and not to be as hard sounding as it is now.

I might be talking nonsense but would be nice to know IF there would be something more to do to tame the (little) cornery feeling when playing the amp.

This might be too loose subject and I understand if there won't be too many replies. But would be ubercool if someone like Andy F. might have something to say on the subject :oops: :D :D :D :?

I made a pedal (HRM circuit) with jfets and it is really nice sounding + super easy to play trough my P1 but it lacks the feel of the D-style amp.

Any ideas ? :D
Last edited by mat on Thu Aug 23, 2007 11:02 am, edited 1 time in total.
mat
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Funkalicousgroove
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Re: hard to play amp - cure ? Clip added

Post by Funkalicousgroove »

Post a pic of your build.
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Funkalicousgroove
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Re: hard to play amp - cure ? Clip added

Post by Funkalicousgroove »

You say that one is harsh and barky?

Are those 225p or 6ps orange drops, or are they 715's?

Have you tried different brands of tubes?
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dogears
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Re: hard to play amp - cure ? Clip added

Post by dogears »

Mat,

Make sure the grid resistor on OD2 is a 150K. Not 180K. It will help.....

Are you sure that the resistor in front of the 22K trimmer for the OD levels is a 200K?? The one after the 470K w/47pf

I'd replace all critical signal path resistors with 1W or 1/2W carbon. Not 1/8w metal.

Not that it matters much, but I would definately reduce the .0012 across the bass pot to .001uf
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Bob-I
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Re: hard to play amp - cure ? Clip added

Post by Bob-I »

What is your bias setting? Your description sounds like possible crossover distortion or oscillation.

The changes mentioned will smooth out the amp, but if you truly have the bark and no sustain, I'd be looking for some wrong, not just subtle tweaking.
groovtubin
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Re: hard to play amp - cure ?

Post by groovtubin »

mat wrote:Ok, now really noob question to the pros :oops:

(I'm not nesessearly talking about my new build :oops: ).
What if You end up with a build (any style amp) that seems to be a quite hard to play ? Sometimes the notes bark loud and there might be a very little sustain. If the voltages are right and wiring and lead dress has been done in a proper way. Tubes would be OK. Right component used...etc.

1. What to suspect to be wrong ?

2. What to try to improve the playability ?

Would You try to lower the voltage to the power tubes or what. (On my build I'm pushing the EL34 with 488V's right now.)

I really love the D-style amps for their accurasy and ability to reproduce slightest nyances of the playing but on the other hand every time I listen Fuch amp clips I cannot but drool for their liquidness and sustain.

My resent HRM build 'sings' very beautifully (better than my nonHRM that more likely howls :? ). The singing is not so loud than on the nonHRM and it is more easily controlable.

Anyway I would like to have little more sustain on my HRM build for it to play little easier and not to be as hard sounding as it is now.

I might be talking nonsense but would be nice to know IF there would be something more to do to tame the (little) cornery feeling when playing the amp.

This might be too loose subject and I understand if there won't be too many replies. But would be ubercool if someone like Andy F. might have something to say on the subject :oops: :D :D :D :?

I made a pedal (HRM circuit) with jfets and it is really nice sounding + super easy to play trough my P1 but it lacks the feel of the D-style amp.

Any ideas ? :D
Did you use (4) ohm tap for the HRM version...BIGGIE... ( using marshall OT w/4-8-16 taps) Sounds phenominal thru a 16 ohm Marshall cab ;) The 4 ohm tap allows it to give up the goods a tad easier.
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mat
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Re: hard to play amp - cure ? Clip added

Post by mat »

Funkalicousgroove wrote:You say that one is harsh and barky?

Are those 225p or 6ps orange drops, or are they 715's?

Have you tried different brands of tubes?
My build is not so harsh anymore but little hard playing. Mainly PS's but couple 715's also. I've swapped lots of tubes - no cure.
Make sure the grid resistor on OD2 is a 150K. Not 180K. It will help.....


It is 150k.
Are you sure that the resistor in front of the 22K trimmer for the OD levels is a 200K?? The one after the 470K w/47pf
Yes.
I'd replace all critical signal path resistors with 1W or 1/2W carbon. Not 1/8w metal.
There has been no 1/8w metals in this build but 0.6w's and those has been replaced with 1w and 2w CF's.
Not that it matters much, but I would definately reduce the .0012 across the bass pot to .001uf
I might try a ceramic in there ?
What is your bias setting? Your description sounds like possible crossover distortion or oscillation.
Bob, that is exactly what I have been suspectin all time (the sound reminds me sometime of a badly biased fuzz face) but the bias seems to give right values when measuring across 1ohm resistor. EL34 488V 30mV(mA) for each tubes. I remember Gary suggesting a largeish caps from biaspot wiper to ground for smoothing the bias supply. I'll try that also.
The changes mentioned will smooth out the amp, but if you truly have the bark and no sustain, I'd be looking for some wrong, not just subtle tweaking.
The barking is nothing extreme but some notes jump out loud. That is not the case with my nonHRM build.
Did you use (4) ohm tap for the HRM version...BIGGIE... ( using marshall OT w/4-8-16 taps) Sounds phenominal thru a 16 ohm Marshall cab The 4 ohm tap allows it to give up the goods a tad easier.
I have 4 and 8ohm jacks on my build. I'm using single Celestion 12-65 8ohm. I've tried both 4 and 8ohm jacks. No cure there. The OT is bassman style replacement.
mat
dogears
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Re: hard to play amp - cure ? Clip added

Post by dogears »

Ceramic is fine Mat.

Make sure your lead dress around the sockets is neat. Check around V2. Move the V2b plate wire next to the cathode wire and the lead going to the back panel too.

Also, do you have a 47pf on the clean master? You must have one there with HRM amps. Try 33ma-34ma on the bias. There is about 2ma of screen current so your real bias point is lower.

.02uf output grid couplers will soften the attack. They are essential with the Marshall output section.

Lastly, add a 33uf 450V filter cap to further decouple your loop circuit. Reduce your loop dropping resistor by a little and add another resistor. Change the Dumbleator recovery amp cathode bypass to 10uf. Change the bootstrap on the cathode follower to 27K and 1.8K from 10K and 1.5K. If you have reverb, make sure the transformer and recovery are also decoupled with their own caps. This is all important.
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Bob-I
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Re: hard to play amp - cure ? Clip added

Post by Bob-I »

Bob-I wrote:What is your bias setting? Your description sounds like possible crossover distortion or oscillation.
Bob, that is exactly what I have been suspectin all time (the sound reminds me sometime of a badly biased fuzz face) but the bias seems to give right values when measuring across 1ohm resistor. EL34 488V 30mV(mA) for each tubes. I remember Gary suggesting a largeish caps from biaspot wiper to ground for smoothing the bias supply. I'll try that also.

That sounds a tad cold to me but I don't have a bias calculator here at work. The "barking" may be the crossover distortion jumping in. Make sure to get the bias up to about 70%.
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Re: hard to play amp - cure ? Clip added

Post by Funkalicousgroove »

If you have 488 on the plates you should be biased around 35mA, if you're running the JJ E34L than you should be closer to 40mA.


Being that you're just a tad on the cold side of bias, you might start there.

If Certain notes are really Jumpy you might consider going back to the 8ohm tap for your NF and installing a trimmer in series with the NF resistor and adjust it until it's liveley but not disproportionate.
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groovtubin
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Re: hard to play amp - cure ? Clip added

Post by groovtubin »

Funkalicousgroove wrote:If you have 488 on the plates you should be biased around 35mA, if you're running the JJ E34L than you should be closer to 40mA.


Being that you're just a tad on the cold side of bias, you might start there.

If Certain notes are really Jumpy you might consider going back to the 8ohm tap for your NF and installing a trimmer in series with the NF resistor and adjust it until it's liveley but not disproportionate.
funny you mention that, in the pic of REAL thing, i SEE a trimmer pot down by the edge of board, no one so far has believed me, i SEE the knurled edge of the wiper adj, am i wrong funk? It makes perfect sense to DIAL in a amp! jp
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Re: hard to play amp - cure ? Clip added

Post by Funkalicousgroove »

Which pic? they all have a trimmer between the PI plates, but I've only seen one with what I describe.
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Re: hard to play amp - cure ? Clip added

Post by dogears »

What?? We all know of that pic.... Late 70s Dumble, pic posted by DOug Roccaforte. No secret there Jim...
groovtubin wrote:funny you mention that, in the pic of REAL thing, i SEE a trimmer pot down by the edge of board, no one so far has believed me, i SEE the knurled edge of the wiper adj, am i wrong funk? It makes perfect sense to DIAL in a amp! jp
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Re: hard to play amp - cure ? Clip added

Post by Funkalicousgroove »

He's talking about #218, but it's a blue e-lytic presence cap, looks like a Blue thumbwheel trimmer.
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