The Amp Garage

Lumox,

Do you have the Schematic for the Old Flame??

It looks like and interesting build.


-George

The HRM 102 Schematic is Great!

Is there a similar schematic available for the Non-HRM Version??

I would guess "Non-HRM 102"

Mickey, Your amps look great. How has the business been going. I am glad you asked about the JFET switching. I used it on a prior build and it works great. I think it is the most "elegant" switching method. My dumble is still on the bench and I only need a few more hours to finish the overdirve sect...

BobW,

Can I trouble you for the updated JPEG schematic?? I do not have the Visio software.


-George

Bob-I, Thanks for the feedback. With the values you have shown, it sounds as if the triode is biased to the "cold" side. I would have expected something like 1.3 volts for the Cathode voltage based on the tube charts and using a "middle" value. I know it is all about trial and error, but it seemed l...

In a document about tips on modifiying a Dumble preamp, it talks about adjusting the bias point of the individual preamp triodes. It said to simply measure the voltage drop across the Plate resistor and divide by the resistance value of the Plate resistor. This would give a current value for the bia...

BobW,

Thanks again for psoting your Schematic. I wanted to remind you to post the updated one when you have a chance.

Your schematic seems to cover all the great suggestions by the experts on this board.


Thanks to All,

George

BobW, It would be great if you could update your schematic with the final changes that you called out in your last post. Your schematic seems to be very close to the "ideal" Hybrid-A "Starting Point" that many people have asked for. What was the final verdict on the Level and Drive pots?? What taper...

BobW,

Please let us now what happens when you try the Linear Pots on the "Drive" and "Level" controls

It looks like you covered most of the changes that have been suggested on the board with the addtions from Dogears in the last thread.


Cheers,

George

Elcabong, I use the J105 JFETs. They are fairly inexpensive and have an "ON" resistance of 3-4 ohms. I also build with Terminal Strips, so I place the JFETs on a separate PC board along with a small RC time delay circuit and a connector. I usually can use the same holes that are used for my terminal...

Just curious if anyone has tried "shunt" swtiching in their amps. I have tried shunt switching with relays and JFETs and it "seems" to work great. The natural place to use it is for turning off the reverb. Most reverb circuits have a series resistance to a mixing stage so this works well. It also ha...

I have been looking for a good single tube reverb circuit and I am excited about trying this one on my latest build. I have a general question about "switching" a reverb circuit ON and OFF. I have heard that it is a good practice to shunt the intput and output to ground when the reverb is OFF. Can I...

Bob, Thanks for all the great postings and being such an active part of this forum. I was just curious if you have a "final" version of the schematic that you use for your Non-HRM amps? I know that you have done a lot of experimenting and testing with both versions. You mentioned in a prior post tha...

DBM, You had asked if "I can turn the Level control up past 5 (12 o'clock)". I am able to do this, but I run a Master Volume as well. I can usually always turn up my amps to full blast, but I only use a pair of 6V6 tubes - approx. 18 watts. I also used a Concertina Splitter on my clone which is kind...

Dan, I am glad that you asked the question about changing the value of the 250K pot to 100K by the addition of a resistor "across" the pot. I too, thought that this would approximate a 100K pot - it does not. It actully creates a weird anti-log variation. I also experimented with the technique of pl...