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A big problem for headroom in the V8 is the power supply for the op amp is only +/- 8volts so you can have clipping with low gain on the op amp. The V5 has +/-15 volt rails and you could up them to...

The Weber AlNiCo will fit without the shielding around the magnet. You could consider the Eminence Legend 10516 as a speaker choice also. The output transformer impedance is really 16 ohms so you may...

Here is a list of things to check and ohmmeter to see if the connections are correct.


With the op amp out you should have C24 C25 and C26 removed with a jumper from pin 3 of the op amp to the...

If you do the mod at post #160 the stock volume pot will be a volume pot again and the tone pot will be a tone pot again with C6 installed. So you won’t have the volume pot acting as a gain control...

Yes just put the resistor across the two outside lugs of the pot to parallel it. I looked at the schematic and originally the signal to the second tube was across a 10k resistor so with adding the...

I wish the schematic mark ups were still on line, oh well. I should remember the mod, but it has been awhile. I don’t recall if the tone pot is a linear or audio (log) taper but there is way more...

I found the mark up and picture to go with the no op amp modification that is part of posting #168. Here are links to them http://i1020.photobucket.com/albums/af330/vactube/noopampmodification.jpg...

The following are instructions and schematics are for a cheep way to add the Belton Digital reverb to the Valve Jr amp, but the Crate is similar so you can basically do the same thing. If you use the...

I am in the process of getting together some reverb kits for three people at this point. The cost is approx 55 bucks for the DIY you assemble the PCB kit using the Belton Digi-Reverb module. I have...

There are a couple of mods posted for how to bypass the op amp #168 here http://www.thefret.net/showthread.php?t=9379&page=9 is one that I posted and there are a few more.

Thinking about your problem with the volume level makes me wonder if it is just the sensitivity of the controls that is the bother. On the volume control you just added maybe a lower value pot would...

If you are thinking about adding a standby switch this Carling switch model 2GG51-73 that they have at Antique Electronic Supply (P-H520) fits right in place of the stock switch...

I have to take some more time to see what effect some of the value changes you are posting would have on the frequency response of the op amp circuit. Changing R10 will have no real effect on this...

Warm or cold bias? Being you are going to over drive the tube you may want to change how the first triode stage is biased. If you look through the posts you should find a link to a web page that goes...

Yes how you are going to connect the pot is correct removing R7 will give you a bit more signal to the control grid it would matter more if you had a master volume at the R16 location for this mod...

It sounds like you are going to keep the exiting volume control as a gain control and then add a volume control after the first triode stage? As stated above in another post I would go with a 100k...

I have posted two sound clips of the Belton Digi-reverb mounted on the PCB I designed installed in a Crate V5 amplifier. It is my son playing with the amplifier connected to a cabinet with two Jensen...

Looking at the input and output of the Digi-reverb I am getting numbers that are different then the data sheet. Part of the problem could be the approx 30 years old Phillips scope I am using, but...

Well I built up a board and first installed it in a Ver 1 VJ combo amp with AC filaments. Couple of problems with that being the first stage triode plate trace runs parallel with the control grid for...

Well I thought I would post what I have for right now. I have the PCB and have installed most of the parts for operation. I tested the FET buffer stage and common emitter stage using two 9 volt...

I have three blank PC boards on order by what things are costing out to be if I had 10 or more people who wanted these the cost would be around 40 to 50 bucks. That would be all the parts on the PCB...

I posted this over at SEwatt and though I would post it here also for anyone thinking about adding reverb.

Well I am up to the point of ordering some boards made, just waiting on getting the...

Maybe the pot is bad or there is a bad solder joint going to one of the leads on the pot. I would look at the connections to the PC board and maybe just reflow them with a soldering iron and a little...

Just to ask did you check the voltages on the op amp pins as I posted before the negative supply is on pin 4 and should be approx -15 volts. Then there is the positive supply on pin 8 which should be...

You could consider just getting rid of the op amp look at post #160 and #168. An op amp can take quite a bit of heat so I doubt you hurt it that way. If you have not replaced the op amp that would be...