Jvm410hjs - Fx Loop Buffered ?

[Dicky5150]

Hi, do any of you knowledgable chaps know if the JVM 410hJS has a buffered fx loop, especially the send side ? Been having some tones issues using a TC Electronic G System, and picked up something on the TC forum about amp fx loops causing problems due to impedance miss matches if the FX send is unbuffered ?

Regards and TIA

Dicky

 

[MonstersOfTheMidway]

That's a good question (I don't know the answer, sorry). I know that the effects loop is mixed into the signal via a preamp tube, but after that I'm not sure.

I can't recall what Santiago said about the Satriani HJS effect loop on this particular topic, but maybe he'll chime in (I'm interested in knowing the answer).

for your thread!

 

[marshallmellowed]

Pretty sure it's OP-Amp buffered.

 

[mickeydg5]

Solid up front and tubed in the rear.

 

[ampmadscientist]

Hi, do any of you knowledgable chaps know if the JVM 410hJS has a buffered fx loop, especially the send side ? Been having some tones issues using a TC Electronic G System, and picked up something on the TC forum about amp fx loops causing problems due to impedance miss matches if the FX send is unbuffered ?

Regards and TIA

Dicky

On my schematic, there is no buffering either on send or return.
(maybe there is a different version...)
http://musiciansroadhouse.com/viewtopic.php?t=11597
But send being a cathode follower, possible to use high level (line level) effects pedals to drive the return hard enough.
Not much there for low level effects, typical of a Marshall effects loop.
Use a pedal with an input level control for the first in the loop,
use a pedal with an output level control for the last pedal in the loop.
At least you can get the level close to what it should be if you do that.

 

[marshallmellowed]

On my schematic, there is no buffering either on send or return.
(maybe there is a different version...)
http://musiciansroadhouse.com/viewtopic.php?t=11597
But send being a cathode follower, possible to use high level (line level) effects pedals to drive the return hard enough.
Not much there for low level effects, typical of a Marshall effects loop.
Use a pedal with an input level control for the first in the loop,
use a pedal with an output level control for the last pedal in the loop.
At least you can get the level close to what it should be if you do that.

The link in your post is to the schematics of a standard JVM, not an HJS (loops are different). Also, there are 2 loops, FX and power amp.

 

[mickeydg5]

The regular JVM410 has tube drive and tube recovery.

 

[Matt_Krush]

The Parallel/Series Effects loop is buffered.
Op amp for the send with low output impedance (100ohm) and a tube stage for the return with high input impedance (>1M).

The Power Amp Loop is not buffered at either end that I see. It is impedance correct, 1k send, 470k return.

 

[tschrama]

any body got the JVM 410hJS and willing to post?

 

[santiall]

Standard JVM:
- Programmable Series/Parallel loop: SEND tube buffered (a cathode follower IS a buffer), RETURN recovery by tube with LINE/INSTRUMENT level switch and MIX control
- Power Amp insert: SEND tube buffered , RETURN into power amp MASTER volume (power amp input). Line level only

JVMHJS:
- Programmable SERIES loop: SEND buffered by the gate circuit (op amp), RETURN recovery by tube. Instrument level only with Return Level control
- Power Amp insert: SEND tube buffered, RETURN into power amp MASTER volume (power amp input). Line level only

 

[Dicky5150]

Thanks for the replies chaps, I’ve been using the power amp insert loop, as it reduces a lot of the noise I’ve been experiencing with the fx loop. I bought a TC bonafide buffer pedal and tried it tonight, to my ear it seemed to make a difference, but I guess I’ll maybe try it again at a gig and see how we go from there.
Cheers,
Dicky

 

[MonstersOfTheMidway]

Standard JVM:
- Programmable Series/Parallel loop: SEND tube buffered (a cathode follower IS a buffer), RETURN recovery by tube with LINE/INSTRUMENT level switch and MIX control
- Power Amp insert: SEND tube buffered , RETURN into power amp MASTER volume (power amp input). Line level only

JVMHJS:
- Programmable SERIES loop: SEND buffered by the gate circuit (op amp), RETURN recovery by tube. Instrument level only with Return Level control
- Power Amp insert: SEND tube buffered, RETURN into power amp MASTER volume (power amp input). Line level only

Thank you, Santiago, for valuable information and taking the time out of your busy day to share.

For those who might not know, "santiall" is the designer of the JVM4 series, JVM2 series, and the Joe Satriani signature JVM410HJS (among other great amps he's designed).

Have a great day.

 

[Sirion]

Hey Dicky5150, what is your verdict on this combination now that you've lived with it for a couple of weeks? I am having a similar problem with a JVM205C and a second-generation (red limited edition) G-System: the D/A converters in front of the amp subtly change the tone colour, which I can live with, but the components put in the fx loop reduces the volume significantly. I know that the loops in my amp are slightly different, but I suspect that a buffer will be the solution in my case, too.

 

[Dicky5150]

Hi, well to be honest I’m still not sure ! I think it has definitely helped, but, the tone I get when I plug into the amp alone is still better than when I use the buffer with my g system in the loop. Having studied some posts on the Tc electronic forum, I’m wondering now if what I should try is a line level shifter, and see if it’s the output from the preamp that’s too hot for the g system. I’ll get there in the end, just taking longer than I’d have hoped !

Regards

Dicky

 

[Sirion]

Great, let me know what you think! I might take the liberty of posting something here as well, once I get around to it (it will probably be a while still, as my guitar stuff fund is depleted at the moment), as well.

 

[Dicky5150]

Just an update, having tried the buffer I then found another Morley device, the FX loop corrector. This drops the signal level between devices. I’ve now got that between the loop send and return (2 channel device) and this has improved things to the point that I’ve removed the buffer altogether. Worth checking out if you’re having loop issues.

 

[MonstersOfTheMidway]

Just an update, having tried the buffer I then found another Morley device, the FX loop corrector. This drops the signal level between devices. I’ve now got that between the loop send and return (2 channel device) and this has improved things to the point that I’ve removed the buffer altogether. Worth checking out if you’re having loop issues.

Hello.
You're the first person I've heard talk about this device; it sounds interesting and promising.

Does the device produce a lot of heat?
The manual states it doesn't use batteries or power adapter (the manual describes it as "passive" in this regard).

Thanks for spreading the news. Good luck with your gear.

 

[Dicky5150]

Hello.
You're the first person I've heard talk about this device; it sounds interesting and promising.

Does the device produce a lot of heat?
The manual states it doesn't use batteries or power adapter (the manual describes it as "passive" in this regard).

Thanks for spreading the news. Good luck with your gear.

Hi, I can’t say I’ve noticed it producing any heat as of yet, though I doubt I’d notice as it’s in the back of my rack, seems to have improved things though. It requires no power, just sits there and does it’s thing !!

 

[spacerocker]

Hi, I can’t say I’ve noticed it producing any heat as of yet, though I doubt I’d notice as it’s in the back of my rack, seems to have improved things though. It requires no power, just sits there and does it’s thing !!

It will be a simple resistor network, or an audio transformer.....