zmix
Well-known member
I remember being very impressed with the Peavey AMR VMP-2 preamp when it first hit the market. I did a a simply tally and realized that the parts inside would cost me more than the entire unit and it had the advantage of being new and under warranty! I was therefore quite happy to learn that PV went on to make a "tube compressor" in a similar package. I was pretty weary of manufacturers who market any old circuit in a box, add a vacuume tube and -voila! "Tube-Compressor". What bullshit. Peavey must have someone on staff who cares about this stuff. I wish I knew more about how these two products came to be - if you know, do tell!
The VC/L-2 uses the same "tube and transformer" topology as the pre.
For the VC/L-2 they remanufactured their own version of the T4-B (which, BTW, they note that they did "at great expense" although these days the EL panels are available at any 99 cent store as nightlights....)
Their mic pre used reichenbach transformers, the VC/L-2 uses something similar, but unbranded, The output transformer has a 3dB down point of 85kHZ. Not too shabby. The power supply is phenominal on this thing, too, it's regulated, clean, and quiet.
After years of looking I finally purchased one of these compressors on ebay, and, naturally, started experimenting with it almost immediately.
I've been around the block a few times with the thing, circuit-wise, and I have some interesting findings.
The original circuit is quite similar to, but not exactly the same as an LA-2A. I decided to modify one channel and leave the other stock, as a 'control group'.
The first thing I did was to redesign the input stage to generate a better distribution of harmonics. I have designed an original circuit that does this perfectly. This change made a phenominal difference in the sweetness of the tone, however there were several problems with this, some new, some old. The 'old' problem is that the sidechain introduces a tremendous amout of harmonic activity into the audio. One side effect of this 'harmonic injection' is that as the gain reduction is increased (oxymoron?) nearly all of the second harmonic is canceled and the tone hollows out. The 'new' problem is that my circuit seemed to have some stability issue, just before clipping it would generate spurious HF energy (8kHZ and higher). I worked on this for way too long, and I suspect it has something to do with the existing PCB layout. In my experience this is a real problem with a lot of Peavey tube gear. In the case of the VC/L-2 at least the channels are built on identical, individual circuit cards, so the channels do have nearly identical behavior. (unlike the 'tube sweetener'...yikes).
I eventually gave up on this modification and instead, I rewired the channel to be identical to the LA-2, right down to the white-follower on the output stage, the DC in the feedback loop and the paralleled tubes in the sidechain. As a final step I should be able to drop in a 12BH7 on the output with no problem.
Does anyone have any experience dealing with the sidechan bleed? My LA-3A has no such problem. Is it the opto? In the VC/L-2 the EL panel is driven by an EL84, which is on a separate daughter board and has a metal shield around it.
The VC/L-2 uses the same "tube and transformer" topology as the pre.
For the VC/L-2 they remanufactured their own version of the T4-B (which, BTW, they note that they did "at great expense" although these days the EL panels are available at any 99 cent store as nightlights....)
Their mic pre used reichenbach transformers, the VC/L-2 uses something similar, but unbranded, The output transformer has a 3dB down point of 85kHZ. Not too shabby. The power supply is phenominal on this thing, too, it's regulated, clean, and quiet.
After years of looking I finally purchased one of these compressors on ebay, and, naturally, started experimenting with it almost immediately.
I've been around the block a few times with the thing, circuit-wise, and I have some interesting findings.
The original circuit is quite similar to, but not exactly the same as an LA-2A. I decided to modify one channel and leave the other stock, as a 'control group'.
The first thing I did was to redesign the input stage to generate a better distribution of harmonics. I have designed an original circuit that does this perfectly. This change made a phenominal difference in the sweetness of the tone, however there were several problems with this, some new, some old. The 'old' problem is that the sidechain introduces a tremendous amout of harmonic activity into the audio. One side effect of this 'harmonic injection' is that as the gain reduction is increased (oxymoron?) nearly all of the second harmonic is canceled and the tone hollows out. The 'new' problem is that my circuit seemed to have some stability issue, just before clipping it would generate spurious HF energy (8kHZ and higher). I worked on this for way too long, and I suspect it has something to do with the existing PCB layout. In my experience this is a real problem with a lot of Peavey tube gear. In the case of the VC/L-2 at least the channels are built on identical, individual circuit cards, so the channels do have nearly identical behavior. (unlike the 'tube sweetener'...yikes).
I eventually gave up on this modification and instead, I rewired the channel to be identical to the LA-2, right down to the white-follower on the output stage, the DC in the feedback loop and the paralleled tubes in the sidechain. As a final step I should be able to drop in a 12BH7 on the output with no problem.
Does anyone have any experience dealing with the sidechan bleed? My LA-3A has no such problem. Is it the opto? In the VC/L-2 the EL panel is driven by an EL84, which is on a separate daughter board and has a metal shield around it.
