Minimalist 4X6L6 100watter

[dogears]

Never use the preamp lnfb when building an HRM. Doesn't sound good IMO. In 99% of real HRM amps, there is no feedback there. Ther eis one known amp with it but it is a really really oddball circuit unlike anything else.

Actually I was referring to the global nfb not the local feedback.

Anyone know how much (in db) the nfb?

I've heard mixed things about the local feedback - is there any consensus?

Thanks for your input.

[Bob-I]

Actually I was referring to the global nfb not the local feedback.

Ahhh.. sorry. DO NOT under any circumstances go without the global feedback. It will simply not bloom and sing like a Dumble should.

Anyone know how much (in db) the nfb?

Typically about 8Db

I've heard mixed things about the local feedback - is there any consensus?

Nope, that's why mines on a switch

[dave g]

This is just my own opinion, but...

I think this amp is a complete waste of time and money. Why spend $1000 in parts and dozens of hours of labor building a one-trick pony when you can just build the real deal and get a million more sounds out of it?

I have wasted enough time and money myself on amps that I ultimately regret building. I hate to see other people make the same mistakes.

[Bob-I]

This is just my own opinion, but...

I think this amp is a complete waste of time and money. Why spend $1000 in parts and dozens of hours of labor building a one-trick pony when you can just build the real deal and get a million more sounds out of it?

I have wasted enough time and money myself on amps that I ultimately regret building. I hate to see other people make the same mistakes.

I disagree. I have several ODS type amps and I find that through a gig I switch off the ODS once or twice. In reality it's not even really necessary, I can just roll back the volume and get the cleans I need.

JMO

[Ed de Jager]

Same here.

[ontariomaximus]

Here is my Minimalist HRM. It is the ODS-101-HRM, with the PAB engaged, no deep switch, no bright switch, no mid boost. Just a pure Overdrive amp, but with pretty decent cleans. Just finished wiring it up and I only have about 15 minutes on it, but it's pretty cool. A couple points - with the PAB, you would never dime the gain (formerly the volume control) it's just too mushy one full bandwidth 12AX7 fully feeding another so there is a voltage divider just before the gain control. The amp also sounded best with the drive dimed, that much was clear to me right off the bat, so a resistor could take the place of the pot. The 500k master could be considered the 1m clean master and 1m OD master in parallel, and there is obviously no need for both.

This feeds a 820/24k PI, then 4x6L6GC for 100w. I'll report more on the sound as my opinion gets fully formed but it's promising, otherwise I wouldn't take the trouble to post this.

I mainly built it as a reference for my Daisycutter circuit, fwiw.

[dogears]

Why the 500K master? The loading on the stack is off.... I'd stick with the 1M. The clean master is in parallel with the pre-od network and not the overall master. Hang a 1M across the pre-od network to simulate that load. It does matter.

You may want to experiment with making this a Bluesmaster lite. The cleans and PAB tones are very versatile and you really could ride the one channel for a whole gig!

Here is my Minimalist HRM. It is the ODS-101-HRM, with the PAB engaged, no deep switch, no bright switch, no mid boost. Just a pure Overdrive amp, but with pretty decent cleans. Just finished wiring it up and I only have about 15 minutes on it, but it's pretty cool. A couple points - with the PAB, you would never dime the gain (formerly the volume control) it's just too mushy one full bandwidth 12AX7 fully feeding another so there is a voltage divider just before the gain control. The amp also sounded best with the drive dimed, that much was clear to me right off the bat, so a resistor could take the place of the pot. The 500k master could be considered the 1m clean master and 1m OD master in parallel, and there is obviously no need for both.

This feeds a 820/24k PI, then 4x6L6GC for 100w. I'll report more on the sound as my opinion gets fully formed but it's promising, otherwise I wouldn't take the trouble to post this.

I mainly built it as a reference for my Daisycutter circuit, fwiw.

[ontariomaximus]

I added the 1m to simulate the clean master at the pre-od. I also changed the 100k resistor feeding the 500k master to 470k to get very close to the 1.1m load presented in the stock amp. I doubt I would ever use the ODS with the master dimed, hence the resistor change vs changing to a 1m pot.

[dogears]

It looks like your 1M is in the wrong spot. It should be across the pre-od net and not on V1a. Hang it from the .047uf cap to ground on V1B.

I added the 1m to simulate the clean master at the pre-od. I also changed the 100k resistor feeding the 500k master to 470k to get very close to the 1.1m load presented in the stock amp. I doubt I would ever use the ODS with the master dimed, hence the resistor change vs changing to a 1m pot.

[ontariomaximus]

It looks like your 1M is in the wrong spot. It should be across the pre-od net and not on V1a. Hang it from the .047uf cap to ground on V1B.

I added the 1m to simulate the clean master at the pre-od. I also changed the 100k resistor feeding the 500k master to 470k to get very close to the 1.1m load presented in the stock amp. I doubt I would ever use the ODS with the master dimed, hence the resistor change vs changing to a 1m pot.

It is just after the .047.

[dogears]

Not in the .tif file you uploaded. It is after the .0047 cap that replaces the tonestack.

It looks like your 1M is in the wrong spot. It should be across the pre-od net and not on V1a. Hang it from the .047uf cap to ground on V1B.

I added the 1m to simulate the clean master at the pre-od. I also changed the 100k resistor feeding the 500k master to 470k to get very close to the 1.1m load presented in the stock amp. I doubt I would ever use the ODS with the master dimed, hence the resistor change vs changing to a 1m pot.

It is just after the .047.

[ontariomaximus]

Thanks for your interest. The 1m after the .0047 is the gain pot, what was formerly known as volume. The 1m resistor added after the .047 was per your recommendation so it went in after the schematic was posted. Can you replace the .tif?

Btw, I have spent some time with it.
Two words: Brown Sound.
There's more to it than that and I'll elaborate in the future.
So far it has greatly exceeded my expectations.

[dogears]

Ahh! Ok... Sorry. I assumed the schematic was final.....

Good job. You can experiment with that .0047 tonestack cap btw. Lots of possibility there. I also like 500pf around the 220K grid resistor. Enhances more upper mids.

Thanks for your interest. The 1m after the .0047 is the gain pot, what was formerly known as volume. The 1m resistor added after the .047 was per your recommendation so it went in after the schematic was posted. Can you replace the .tif?

Btw, I have spent some time with it.
Two words: Brown Sound.
There's more to it than that and I'll elaborate in the future.
So far it has greatly exceeded my expectations.

[ontariomaximus]

Getting back to the minimalist HRM...Here is a clip. It is an amp with the minimalist HRM circuit described earlier in the thread, this time with a cathode bias EL34 output stage (B+ about 470VDC). The amp also a clean channel based on the Bad Cat Hot Cat 30. Each channel feeds one side of the LTPI.

http://www.youtube.com/watch?v=28rkoChtts4

[ampdoc1]

Ontario,

While the playing and tone on your clip are very good for that style, I didn't hear anything there that would have suggested to me that was a Dumble amp. I know Dumbles can shread if pushed, but why copy a Dumble if you're going for an SLO type sound?

Just saying,..

ampdoc1