Killing the hash PO

[Structo]

Yeah, I'm probably grasping at straws but I remember reading somebodies post about the TL072 opamp chip that the Ironsounds loop comes with and that the guy had improved the way fidelity of the loop by changing the chip.
Unfortunately, I can't remember which chip he went to.

From reading it seems that the OPA2134P opamp get high marks from the Hi Fi crowd as far as speed and THD goes.

I do believe what you guys are saying about the loop but this certainly can't hurt anything to try it.

[butwhatif]

LM6172 is a good one. Upgrading the chip(s) generally means you'll hear the flaws more--

[Deric]

Didn't you say the "hash" is still there when you bypass the loop?

[frischmann]

Tom,
Have you thought of making a stethascope (sp) using a battery powered amp and a resistor tied to a chopstick? It's cool to help localize sound irregularities.

It's not as cool at finding carrier waves etc as a real scope but it can help...

[greiswig]

Yeah, I'm probably grasping at straws but I remember reading somebodies post about the TL072 opamp chip that the Ironsounds loop comes with and that the guy had improved the way fidelity of the loop by changing the chip.
Unfortunately, I can't remember which chip he went to.

From reading it seems that the OPA2134P opamp get high marks from the Hi Fi crowd as far as speed and THD goes.

I do believe what you guys are saying about the loop but this certainly can't hurt anything to try it.

That'd be me, Tom. I put a Linear Audio chip in there. I tried a 2134P, too...couldn't hear the difference between those two at all. In some audio circuits, I've heard a difference between the two...but mostly on the high end. I don't think a guitar amp has the bandwidth to show that difference. Anyway, both chips sounded a little clearer than the stock chip, but not by much.

[butwhatif]

what is this 'hash' anyway, what is this thread about? circuit noise? improper gain structure? inverse mojo? ghosts?

[Structo]

Heheheheh,
Yeah, all of the above.

Just an ongoing problem I've had with this amp.
Overall it sounds great but it has a bit of fizz or hash that rides on the notes.

Eventually I'll track it down but I have been picking the brains of the smart guys here.

Deric, on the last time I was trouble shooting it seemed to be clear with the loop bypassed.
It could even be a pedal that is doing it.
I just need to devote some serious time in a day to better track it down.

[butwhatif]

it should be easy to figure out where that is coming from

-re an ic based efx loop, prob not the greatest idea, as the signal would have to be knocked down considerably to access it, as the chip couldn't drive the large peak voltage swing, and then brought up considerably to drive straight into an PI pulling up the noise floor with it -
as u know sometimes the toughest thing is keeping the original tone thru large gain shifts, every circuit behaves as a filter somewhat due to impedance issues, etc

[Structo]

I was reading over at Metro and Steve (SDM) commented about FX loops that use an IC.

He said:

The opamps can only put out a bit less signal swing then their supply voltage which means under 30V peak to peak signal swing before they'll clip the signal flat off. The original signal fed to the loop can easily be more than twice that voltage peak to peak swing, so as long as the opamps are there, the loop cannot pass the signal along unclipped past under 30V peak to peak out.

Makes sense, and if that is true then the Ironsounds loop is clipping the signal.
Metro wants $90 for their two transistor loop...
I know a Dumbleator would probably be the best alternative but I don't really want an outboard loop.
And, my chassis is already crammed full soooo......

Rough example simulated below to demonstrate this clearer, Red is what would be hitting PI normally (no loop), Green is what the Marshall loop puts out under same circumstances to PI.

[butwhatif]

I rest my case,

[bluesfendermanblues]

Why don't you just build a Kleinulator, which use two FET trasistors and sound really great. IMHO the best alternative to a real dulmblator.?

[erwin_ve]

Why don't you just build a Kleinulator, which use two FET trasistors and sound really great. IMHO the best alternative to a real dulmblator.?

A while back I made a comparison between the D-lator and Kleinulator:

Here it is: www.e-noize.nl/goodies/Dlator_vs_Klein.mp3
It's a large file(13,5 Mb) so it could take a while!

Track________________Kleinulator__________Dumblelator
My one and only…______0.00-0.42___________0.45-1.22
Funky vamp___________1.24-2.00___________2.01-2.39
Landau thing___________2.41-3.23__________3.25-4.28
Don’t need no Mayor_____4.31-5.05__________5.06-5.48
Talk to your son_________5.52-6.33__________6.37-7.19

All tracks are recorded with same settings and no fx in the loop. Also no eq and no other fx are added afterwards.
So it may feel a little to direct, however it's the best method to compare IMHO.
All tracks were normalized, initially I thought it had no volume issues. But the Dumbleator is compressing a fair amount, that's why it feels louder.
The D-lator has less clipping issues.

BTW; My amps OD channel sounds a bit bassheavy, 2 weeks ago I did a OD entrance mod (0,05uF//4,7M) it's much better now .

[bluesfendermanblues]

Why don't you just build a Kleinulator, which use two FET trasistors and sound really great. IMHO the best alternative to a real dulmblator.?

A while back I made a comparison between the D-lator and Kleinulator:

Here it is: www.e-noize.nl/goodies/Dlator_vs_Klein.mp3
It's a large file(13,5 Mb) so it could take a while!

Track________________Kleinulator__________Dumblelator
My one and only…______0.00-0.42___________0.45-1.22
Funky vamp___________1.24-2.00___________2.01-2.39
Landau thing___________2.41-3.23__________3.25-4.28
Don’t need no Mayor_____4.31-5.05__________5.06-5.48
Talk to your son_________5.52-6.33__________6.37-7.19

All tracks are recorded with same settings and no fx in the loop. Also no eq and no other fx are added afterwards.
So it may feel a little to direct, however it's the best method to compare IMHO.
All tracks were normalized, initially I thought it had no volume issues. But the Dumbleator is compressing a fair amount, that's why it feels louder.
The D-lator has less clipping issues.

Great selection of well played riffs - (the klien is first and dumblator second, right?).

I cant quite hear a difference in regards to compression, but the second part of each riff (the dumblator?) seems a little brighter, which I tend to prefer. Could this brightness stem from different cables or ?

However, the Klein could easily be modified to a little more brightness with a small cap.

Besides brightness I cannot reaal hear a difference between the two clips. Love your playin!

[erwin_ve]

Great selection of well played riffs - (the klien is first and dumblator second, right?).

I cant quite hear a difference in regards to compression, but the second part of each riff (the dumblator?) seems a little brighter, which I tend to prefer. Could this brightness stem from different cables or ?

However, the Klein could easily be modified to a little more brightness with a small cap.

Besides brightness I cannot reaal hear a difference between the two clips. Love your playin!

Thnx!
Time codes are mentioned in previous post to make sure which part is Klein and dlator.

Brighter=more overtones!

The same cables were used.
The difference in recording maybe subtle, but it feels very different.

[heisthl]

Heheheheh,
Yeah, all of the above.

Just an ongoing problem I've had with this amp.
Overall it sounds great but it has a bit of fizz or hash that rides on the notes.

Eventually I'll track it down but I have been picking the brains of the smart guys here.

Deric, on the last time I was trouble shooting it seemed to be clear with the loop bypassed.
It could even be a pedal that is doing it.
I just need to devote some serious time in a day to better track it down.

I'm too lazy to go back and read all the posts - Are the O.T. leads bleeding to some signal wire in the build - I've had problems with the OT secondary wires (going to the Z selector) being too close to the PI grid wires causing "hash".