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Laney GH100L & 6550 tubes, also some other stuff...
Greets! I've been a long time member of AX84 forums, diystompboxes and various other, but in the end never managed to stop by here, and eventally I'm here, of course with a question! 
So.
The Laney GH100L. A really really good amp. I saw the topic here for more gain, really... This amp has plenty of gain on tap! I'm not using the drive channel at all, the gain knob dimmed works good enough for me!
A little review:
Pro's:
* pretty good build quality, haven't had any problems with it in years
* sounds good stock
* plenty of gain
* simple and straightforward
* really good distortion sound, very "natural" sounding, not overcompressed modern metal chugga chugga (it's a jcm800 knockoff after all)
* easily use EL34 or 6L6, just switch the bias position in the back, but biasing is needed by expert of course
* has soft start, I guess it has to count for something good?
* has effects loop that is switchable - series, parallel or none, also if you use the switch in series or parallel position, and still not use the eff loop (no jacks plugged in) - the eff loop is still bypassed totally (cool!)
* looks good
* costs peantus!!!! (especially compared to JCM series amps)
Con's:
* noisy, probably cheaply done filtering
* pcb is not exactly easy to take out and mess around (err, mod or change components)
* maybe the power tubes are too close to each other?
* it is simple and all, but kind of limited in terms of clean sounds, but who cares for that with this amp?!?!
* no bias points, no 1ohm resistors or easily accesible bias options (bummer!)
* soft start looks like a potential malfunction area, relays and stuff, complication indeed, though I never had problems with that!
* effects loop is done via opamps, maybe not the sweetest idea, but I cannot comment on sound quality of it
* no reverb
Other remarks:
Have no clue about the stock tubes, I replaced all the 12AX7's to Tung-sol and they sure are sweet sounding. Have tried EHX EL34s in the output - they sound plain, boring and last long, also cheap and work well, why not?! JJ E34L - pretty good, very nice bottom end, more headroom, but they are poorly built, after 3 months one of the tubes bought the farm, I had bad experiences with JJ E34L's before too. Sovtek 6L6 (or some other brand?) - interesting, a bit diffrent amp with them, less mids, less compression and more definition. Tung-sol EL34B - fat and tight - my current favorites.
Now, I have been craving for a Sunn Model T, and while I know this amp won't cut it, I'm trying to get a little bit more out of it, and I think there is room for improvement without butchering the insides alot.
Schematic:
laneygh100l.pdf
I have paralled some caps, actually piggbacked them since accessing the PCB is not that easy.
C15 and C19 are piggybacked with 100nF caps.
I reckon the whole preamp circuit limits the bass enough not to create problems, and I was right, increasing the capacitance of those coupling caps did something to the low frequency spectrum, but have not turned amp into woofy mud, more bass for sure!
I thought of trying out 6550s in the amp, but I'm not quite sure if that is doable.
I've emailed the Laney corporation and got some info: (!!)
This is my question:
Hello, Is the power transformer of GH100L suitable for 6550's current draw? I am thinking of trying 6550's in the GH100L and since it's an EL34 capable amp, I reckon it can withstand the higher heater current draw from the 6550s, but would like to be certain I won't damage the amp. I suppose the bias range for 6550 could be a problem with GH100Ls bias circuitry, should I start with the 6L6 position, since it has different bias range than the EL34s Warm greets from Croatia, Branimir
And the answer:
Hi Branimir,
Thanks for the email, I have spoken to our in house engineers, who have stated the following:
“We haven't tried it so can’t recommend it; but the increased current will probably just be tolerated by the transformer.
Bias I don’t know off hand what it will need to be but certainly the 6L6 position will be the closest to start from.”
Okay, now I need experties of the forum members.
Are any other mods needed to fit this amp with 6550's? I'm guessing 6550's need less negative voltage for bias (around -55V, right?), and I won't be able to get into that territory not even with a switch in the 6L6 bias position (as I noticed, the bias switch only switches the resistor, so you get different negative voltage ranges!), increase value of R41?
Also, I would like to know how to decrease the noise in the preamp? Increase filtering caps? C8 and C11? Higher value?
I appriciate your comments, observations, infos!
ps: I play a Les Paul with P90s tuned to B standard, if anyone cares!
So.
The Laney GH100L. A really really good amp. I saw the topic here for more gain, really... This amp has plenty of gain on tap! I'm not using the drive channel at all, the gain knob dimmed works good enough for me!
A little review:
Pro's:
* pretty good build quality, haven't had any problems with it in years
* sounds good stock
* plenty of gain
* simple and straightforward
* really good distortion sound, very "natural" sounding, not overcompressed modern metal chugga chugga (it's a jcm800 knockoff after all)
* easily use EL34 or 6L6, just switch the bias position in the back, but biasing is needed by expert of course
* has soft start, I guess it has to count for something good?
* has effects loop that is switchable - series, parallel or none, also if you use the switch in series or parallel position, and still not use the eff loop (no jacks plugged in) - the eff loop is still bypassed totally (cool!)
* looks good
* costs peantus!!!! (especially compared to JCM series amps)
Con's:
* noisy, probably cheaply done filtering
* pcb is not exactly easy to take out and mess around (err, mod or change components)
* maybe the power tubes are too close to each other?
* it is simple and all, but kind of limited in terms of clean sounds, but who cares for that with this amp?!?!
* no bias points, no 1ohm resistors or easily accesible bias options (bummer!)
* soft start looks like a potential malfunction area, relays and stuff, complication indeed, though I never had problems with that!
* effects loop is done via opamps, maybe not the sweetest idea, but I cannot comment on sound quality of it
* no reverb
Other remarks:
Have no clue about the stock tubes, I replaced all the 12AX7's to Tung-sol and they sure are sweet sounding. Have tried EHX EL34s in the output - they sound plain, boring and last long, also cheap and work well, why not?! JJ E34L - pretty good, very nice bottom end, more headroom, but they are poorly built, after 3 months one of the tubes bought the farm, I had bad experiences with JJ E34L's before too. Sovtek 6L6 (or some other brand?) - interesting, a bit diffrent amp with them, less mids, less compression and more definition. Tung-sol EL34B - fat and tight - my current favorites.
Now, I have been craving for a Sunn Model T, and while I know this amp won't cut it, I'm trying to get a little bit more out of it, and I think there is room for improvement without butchering the insides alot.
Schematic:
laneygh100l.pdf
I have paralled some caps, actually piggbacked them since accessing the PCB is not that easy.
C15 and C19 are piggybacked with 100nF caps.
I reckon the whole preamp circuit limits the bass enough not to create problems, and I was right, increasing the capacitance of those coupling caps did something to the low frequency spectrum, but have not turned amp into woofy mud, more bass for sure!
I thought of trying out 6550s in the amp, but I'm not quite sure if that is doable.
I've emailed the Laney corporation and got some info: (!!)
This is my question:
Hello, Is the power transformer of GH100L suitable for 6550's current draw? I am thinking of trying 6550's in the GH100L and since it's an EL34 capable amp, I reckon it can withstand the higher heater current draw from the 6550s, but would like to be certain I won't damage the amp. I suppose the bias range for 6550 could be a problem with GH100Ls bias circuitry, should I start with the 6L6 position, since it has different bias range than the EL34s Warm greets from Croatia, Branimir
And the answer:
Hi Branimir,
Thanks for the email, I have spoken to our in house engineers, who have stated the following:
“We haven't tried it so can’t recommend it; but the increased current will probably just be tolerated by the transformer.
Bias I don’t know off hand what it will need to be but certainly the 6L6 position will be the closest to start from.”
Okay, now I need experties of the forum members.
Are any other mods needed to fit this amp with 6550's? I'm guessing 6550's need less negative voltage for bias (around -55V, right?), and I won't be able to get into that territory not even with a switch in the 6L6 bias position (as I noticed, the bias switch only switches the resistor, so you get different negative voltage ranges!), increase value of R41?
Also, I would like to know how to decrease the noise in the preamp? Increase filtering caps? C8 and C11? Higher value?
I appriciate your comments, observations, infos!
ps: I play a Les Paul with P90s tuned to B standard, if anyone cares!