Bob-I wrote:I haven't had a chance to listen to your clip yet, but I switched my reverb to the one tube in Norm's layout. Sounds far better than the Fender reverb I had, but the biggest improvement was that the amp itself sounds better. It appears that there's less affect on the amps tone.
At first I felt that it was a bit weak so I paralleled 2 tubes to add depth. As it turns out there's plenty without this so I'll be putting it back soon.
A lot of the difference is the size of the mix resistor. In this application, smaller is better. BTW, the R10 on the schematic below should be 2W from 27K to 47K.
Bob-I wrote:I haven't had a chance to listen to your clip yet, but I switched my reverb to the one tube in Norm's layout. Sounds far better than the Fender reverb I had, but the biggest improvement was that the amp itself sounds better. It appears that there's less affect on the amps tone.
At first I felt that it was a bit weak so I paralleled 2 tubes to add depth. As it turns out there's plenty without this so I'll be putting it back soon.
A lot of the difference is the size of the mix resistor. In this application, smaller is better. BTW, the R10 on the schematic below should be 2W from 27K to 47K.
Interesting... that's a different version than I used. Mine didn't have the R10 at all. I don't quite understand why it changes the mix, maybe you can explain.
I won't be able to make any changes for a few weeks, business travel, heading to Japan but when I get back I surely try that additional resistor.
I listened to the clip you posted, very nice. Just that little reverb to add some depth to the tone but not overpowering. That's just about the same depth as I get with the control on 1:00.
Bob-I wrote:I haven't had a chance to listen to your clip yet, but I switched my reverb to the one tube in Norm's layout. Sounds far better than the Fender reverb I had, but the biggest improvement was that the amp itself sounds better. It appears that there's less affect on the amps tone.
At first I felt that it was a bit weak so I paralleled 2 tubes to add depth. As it turns out there's plenty without this so I'll be putting it back soon.
A lot of the difference is the size of the mix resistor. In this application, smaller is better. BTW, the R10 on the schematic below should be 2W from 27K to 47K.
Interesting... that's a different version than I used. Mine didn't have the R10 at all. I don't quite understand why it changes the mix, maybe you can explain.
I won't be able to make any changes for a few weeks, business travel, heading to Japan but when I get back I surely try that additional resistor.
I listened to the clip you posted, very nice. Just that little reverb to add some depth to the tone but not overpowering. That's just about the same depth as I get with the control on 1:00.
In the Fender reverb (as implemented in the old blackface amps). The mix resistor was 3M3. THis is extremely large and really has an effect on the overall tone. THis was the reason why Fender added the cap across the resistor was to gain back some highs. It increases the Miller effect in the recovery stage (think this is right, need to check Malvino ). In the one tube arrangement, the mix is only 100K and has much less effect on the overall tone of the amp. I have checked this by placing a jumper on and off the 100K to determine its effect and it negible.
Gary
Located in the St Croix River Valley- Afton, MN
About 5 miles south of I-94
aka K0GWA, K0 Glas Werks Amplification www.glaswerks.com
Bob-I wrote:I haven't had a chance to listen to your clip yet, but I switched my reverb to the one tube in Norm's layout. Sounds far better than the Fender reverb I had, but the biggest improvement was that the amp itself sounds better. It appears that there's less affect on the amps tone.
At first I felt that it was a bit weak so I paralleled 2 tubes to add depth. As it turns out there's plenty without this so I'll be putting it back soon.
Yesterday I switched the Reverb in my Deluxe Reverb II clone. However I kept the parallel 12AT7 at the Reverb drive. I just replaced the 3M3/10pf combo with a 100k resistor, the 0.003uF coupling cap for a 0.01uF and the 100kB Reverb pot for a 1MB (didn't have a 2MB). And of course I took out the additional gain stage that Fender uses with its reverbs.
Everything Bob-I and others said about that reverb - it is true. I never put my Fender reverb above 2-3 on the knob so everything upwards of 3 was useless to me. With the 1 tube reverb I can use the whole range. This change also solved two other problems - one was an oscillation which was even noticeable in the clean channel (similar problem to what ElectronAvalanche described in another post) - second was that the bass significantly tightened up. Good mod. Thanks to everyone for the contributions.
BTW: I may try to parallel both tube sections in the recovery stage for a little more reverb if I want.
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 shunt the Input of this circuit at the junction of C4 & R3 and the Output at the junction of C3 and the 2M potentiometer.
I think the output should be OK, but I am concerned that I may be creating a "Low Pass" filter with the 500pf cap (C4) with this scheme.
I have another amp that has a Fender reverb circuit where I have used JFETs to switch the Reverb ON and OFF and I think that this may be a problem. I will try it to verify, but I was curious if anybody else has faced this problem.
I could always just shunt the output, but this will mean that I am always driving the tank even when the reverb is disengaged.
By the by, there is one additional component that can be added that really helps the one tube circuit.
Add a 0.1uf 630V cap to ground at the junction of R10 and the transformer. This increases the gain of the reverb drive by putting the top of the primary at AC ground.
Gary
Located in the St Croix River Valley- Afton, MN
About 5 miles south of I-94
aka K0GWA, K0 Glas Werks Amplification www.glaswerks.com
I used 4k7 for R10 and added a 22µ to gnd instead of the 0.1 630V. B+ for the reverb recovery is derived from this node via a 22k/22µ.
Is the first 22µ already overkill?
Really depends what is feeding the first 22uf cap.
I used to derive my reverb supply from the screen supply via a 27K resistor. I tried both a 10uf and the .1uf. Sonically I could not hear a difference. The .1uf was easier to implement so it was a logical choice .
The key is to get the supply side of the tranny to AC ground.
Gary
Located in the St Croix River Valley- Afton, MN
About 5 miles south of I-94
aka K0GWA, K0 Glas Werks Amplification www.glaswerks.com
). In the one tube arrangement, the mix is only 100K and has much less effect on the overall tone of the amp. I have checked this by placing a jumper on and off the 100K to determine its effect and it negible.
