Valve power amps

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  • dindudedindude Frets: 8534
    Rocktron also do the velocity 100 for the same sort of price as the Art.
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  • Danny1969;211192" said:
    In terms of design you don't need any great bandwidth for guitar, there's very little going on under 80hz or so and not much above 6K . The cost of stereo power amps is a lot because of the increased component count, basically it's 2 amps in one box even if it's not a duel monoblock design and they are made in much smaller numbers. 

    I always felt gigging a modeller into solid state amps was a bit harsh. I used a Rotel amp, a Marshall Valvestate and a homebrew amp I built. I wasn't happy until I spent the money on a valve power amp ..... there's something about the ouput transformer in a valve design that filters off the nasties and harshness. I've often wondered if an SS amp might benefit from a transformer on the output stage even though it doesn't need one. A simple 1:10 and 10:1 back again, not to change any transfer impendence but to benifit from the effects of passing an audio signal through a transformer. That's where some of the mojo is in my opinion, it's not just the valves but the transformers. 
    A bandit has a transformer. I don't know tech specs, but the one in mine looks like something in a valve amp.

    I used to love seeing the toroidal bitch in my old Laney.
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  • jpfampsjpfamps Frets: 2723
    I find myself desiring a mono 40W+ valve power amp, preferably 1U and not too heavy (or pricey). Does such a thing exist?

    I know there's the Marshall 20/20, but it's stereo. I can live with that if need be, but I'd much rather have a straight mono amp (the 20/20 can't be bridged). The Deep switch is a definite bonus, mind.

    There's also the R&R SOLO (of which I believe there's one in the country which used to be mine), but that fails on the price front mainly because it's a full-on two-channel amp.

    Anything else?
    A 1U 40W power amp will be a tight squeeze, and probably not that sensible from a thermal management point of view.

    Also unless you use two output transformers then you won't get a 40W EI laminated output transformer in 1U. There are now some toroidal output transformers available which may fit, but these are generally expensive.


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  • jpfampsjpfamps Frets: 2723
    Danny1969 said:

    In terms of design you don't need any great bandwidth for guitar, there's very little going on under 80hz or so and not much above 6K . The cost of stereo power amps is a lot because of the increased component count, basically it's 2 amps in one box even if it's not a duel monoblock design and they are made in much smaller numbers. 

    I always felt gigging a modeller into solid state amps was a bit harsh. I used a Rotel amp, a Marshall Valvestate and a homebrew amp I built. I wasn't happy until I spent the money on a valve power amp ..... there's something about the ouput transformer in a valve design that filters off the nasties and harshness. I've often wondered if an SS amp might benefit from a transformer on the output stage even though it doesn't need one. A simple 1:10 and 10:1 back again, not to change any transfer impendence but to benifit from the effects of passing an audio signal through a transformer. That's where some of the mojo is in my opinion, it's not just the valves but the transformers. 

    I would agree that the output stage of a valve is what gives it the "valve" sound; hybrid amps with SS pre-amps and valve output stages (eg the 70s Musicman amps), sound like valve amps to me, whereas the converse don't.

    Some of the very early transistor guitar amps had output transformers (and even interstage transformers), although they didn't generally sound great.

    Dave Peterson developed a SS amp with a transformer in it to help emulate a valve amp (I think they were called RIF amps). Not sure if they made it into production.

    Extending HF bandwidth in a output transformer over and above the audio bandwidth is important if you are using negative feedback to avoid ringing, or worse oscillation. In my experience this is a real phenomenon in valve guitar amps.
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  • digitalscreamdigitalscream Frets: 26453
    jpfamps said:
    A 1U 40W power amp will be a tight squeeze, and probably not that sensible from a thermal management point of view.

    Also unless you use two output transformers then you won't get a 40W EI laminated output transformer in 1U. There are now some toroidal output transformers available which may fit, but these are generally expensive.


    As I said, the R&R SOLO manages it - 50W, 2-channel in 1U. Pretty awesome little amp that too. I never noticed it getting that hot when I had one, either.

    I'm looking at bass amps at the mo; the Peavey Tour 450/700 amps look pretty good...enough tonal tweakery to get around the fact that it's probably not got that low-end whump I get from using my Jet City as a power amp.
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  • jpfampsjpfamps Frets: 2723
    edited April 2014
    jpfamps said:
    A 1U 40W power amp will be a tight squeeze, and probably not that sensible from a thermal management point of view.

    Also unless you use two output transformers then you won't get a 40W EI laminated output transformer in 1U. There are now some toroidal output transformers available which may fit, but these are generally expensive.


    As I said, the R&R SOLO manages it - 50W, 2-channel in 1U. Pretty awesome little amp that too. I never noticed it getting that hot when I had one, either.

    I'm looking at bass amps at the mo; the Peavey Tour 450/700 amps look pretty good...enough tonal tweakery to get around the fact that it's probably not got that low-end whump I get from using my Jet City as a power amp.
    Not seen the R&R amps.

    The 50W amps does indeed employ torodial mains and output transformers (and indeed choke by the looks of it).

    The valves are mounted horizontally outside the main chassis, with fan cooling, which is a very sensible arrangement as hot air is not blown through the chassis, although I am generally not a huge fan of side venting in rack gear, this can be accomadated.

    Looks an elegant design.
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  • drwiddlydrwiddly Frets: 911
    If you can find one used and are OK with SS, then the Rocktron Velocity 300 is a very good power amp. Can be bridged for 300w into 8ohms and the definition and reactance controls add a bit of fine tuning. Not far off a Matrix IMHO and I have both.
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  • digitalscreamdigitalscream Frets: 26453
    Danny1969 said:

    I used to use the 20/20 ... it's a sweet little amp but has some problems. Air intake is from the side and in a regular rack it can overheat. At least mine did till I modded the rack. It's also not the loudest of amps either, it was enough for me but you could run into problems in certain situations
    I ended up getting one anyway - £300 delivered on eBay. Perhaps not the best deal, but I was being impatient ;) 

    I've only tried it at home, so I can't really tell what the volume's like - I managed to get it up to just under half way with the 11R's volume on 6.5, and it was at the extreme end of home volume. I suspect it's going to depend on what the input headroom's like, but I think it's going to be OK if I run it almost flat-out. I've gigged OK with a Jet City 20W before (albeit with a bit of a lack of headroom), and I can't imagine that was capable of putting out much more than 30W at meltdown settings.

    Interestingly, my 20/20 doesn't have any side-intakes - it's got an intake at the front next to one of the transformers, and exhaust at the back. Did they have more than one version?
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  • bignormbignorm Frets: 191
    edited May 2014
    I've only just come across this thread, so apologies for resurrecting it.
    A small footprint valve power amp is the holy grail as far as i'm concerned and have been looking for a way of reducing my rack in size for a couple of years now.
    I use a JMP-1 into a Peavey Classic 60 x 60 power amp which is 3u high for a good reason
    It has three transformers in it, 3 ecc83's and four 6l6's standing up right
    There's no over heating problems with this design as the cooling is done from a large fan at the back of the rack which draws air from the vents at the front across the valves and out the back.
    image
    The nice thing about this power amp is you can run it in mono by just using the left input and turning the right input gain right down.
    It senses no load on the right hand side and turns that side off.
    I've seen mono 120 watt versions on this amp but they are pretty scarce
    Back in the heyday of rack systems, bass player used to run these amps as well as guitarists coz they sound pretty pokey.
    The JMP-1 sounds great with this power amp and the peavey definitely makes a huge difference to the sound coz when i'm in lazy mode at rehearsals, i use a little EH Magnum 44 power amp instead of lugging in the peavey.
    Although the magnum is loud enough to gig with, it doesn't have that warmth or depth of sound you get with the valve power amp.
    You can pick these power amps up for a lot less than £300 and they are worth it mate, mines never let me down ever.
    Its a great amp but I wish there was something out there that would do the same job with less weight.


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  • digitalscreamdigitalscream Frets: 26453
    @bignorm - yes, I had one of those years ago. In fact, it's entirely possible you bought yours from me back on MR ;) It was definitely a great-sounding bit of kit...I used it with an ADA MP-1 (although I never realised it could be run in mono). 

    My complaints with it are nothing to do with the sound - height and weight, really. Comparing it to the 20/20, it's 3U vs 1U and 15kg vs 6kg. I'm a broken shell of a human being, so lugging that around would probably kill me ;)
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  • bignormbignorm Frets: 191
    It could well be your old amp coz I bought it from someone on the MR website.
    I've owned two over the years, the first one was a 120 x120w and the second was this one.
    I found out about the mono switching thing from peavey usa, its not well documented.
    I used to put a dummy load on the right hand side until I found out you can do this.



    @bignorm - yes, I had one of those years ago. In fact, it's entirely possible you bought yours from me back on MR ;) It was definitely a great-sounding bit of kit...I used it with an ADA MP-1 (although I never realised it could be run in mono). 

    My complaints with it are nothing to do with the sound - height and weight, really. Comparing it to the 20/20, it's 3U vs 1U and 15kg vs 6kg. I'm a broken shell of a human being, so lugging that around would probably kill me ;)

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  • ClarkyClarky Frets: 3261

    the Marshall 8008 Valvestate is a great power amp. 80W a side, and can bridge to a mono 160W

    if you can find one you can find one they go for less than £300..

    mine's been awesome.. I've toured it silly for more than a decade and it only failed once [after some particularly rough handling by airport baggage handlers].. for tone, power and reliability I'd highly recommend them

    play every note as if it were your first
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  • digitalscreamdigitalscream Frets: 26453
    Clarky said:

    the Marshall 8008 Valvestate is a great power amp. 80W a side, and can bridge to a mono 160W

    if you can find one you can find one they go for less than £300..

    mine's been awesome.. I've toured it silly for more than a decade and it only failed once [after some particularly rough handling by airport baggage handlers].. for tone, power and reliability I'd highly recommend them

    I didn't think it could do bridged? The problem I have with the 8008 is that it's 80W per side at 4 ohms; if I run my cab stereo, then it's 16 ohms per side and I'll probably get about 20W per channel which isn't really enough for a solid state amp in terms of volume (I think it equates to a 6dB drop either side).
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  • ClarkyClarky Frets: 3261

    I've run my 4x12 cabs 4, 8 [1 cab in stereo] and 16 ohm through it and it's been fine..

    the 8008 is majorly loud

    play every note as if it were your first
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  • digitalscreamdigitalscream Frets: 26453
    Clarky said:

    I've run my 4x12 cabs 4, 8 [1 cab in stereo] and 16 ohm through it and it's been fine..

    the 8008 is majorly loud

    Fair enough. Oh, well...I've got the 20/20 now. I may trade it up for a solid state amp at some point...if I do, it'll probably be a Matrix (GT800FX, I'd imagine).
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  • ClarkyClarky Frets: 3261

    if you do take the Matrix route, go for the GT1000FX because it's a newer model than the GT800 and has the more valve-like feeling

    in the past I've used:

    Marshall 8008 [still have it and love it]

    Matrix GT1000FX [which is now my main power amp]

    Mesa Boogey Strategy 400 [huge, heavy, loud and awesome.. but you need a wheelbarrow to move it around]

    Marshall EL34 100/100 [which was surprisingly not much different from the 8008.. sure it was a superb, amp but I expected it to be so much better than the 8008.. and it just wasn't.. kinda popped the EL34 GAS bubble that I'd had for a year of so leading up to that moment]

    play every note as if it were your first
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  • ICBMICBM Frets: 71957
    jpfamps said:
    Not seen the R&R amps.

    The 50W amps does indeed employ torodial mains and output transformers (and indeed choke by the looks of it).

    The valves are mounted horizontally outside the main chassis, with fan cooling, which is a very sensible arrangement as hot air is not blown through the chassis, although I am generally not a huge fan of side venting in rack gear, this can be accomadated.

    The three toroids in it are the OT and two separate PTs for the HT and LT.

    However, I have to say that I can't vouch for the reliability of this amp. The one I've had experience of appears to be a prototype, but still had some major issues - although I don't think heat-related.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • jpfampsjpfamps Frets: 2723
    ICBM said:
    jpfamps said:
    Not seen the R&R amps.

    The 50W amps does indeed employ torodial mains and output transformers (and indeed choke by the looks of it).

    The valves are mounted horizontally outside the main chassis, with fan cooling, which is a very sensible arrangement as hot air is not blown through the chassis, although I am generally not a huge fan of side venting in rack gear, this can be accomadated.

    The three toroids in it are the OT and two separate PTs for the HT and LT.

    However, I have to say that I can't vouch for the reliability of this amp. The one I've had experience of appears to be a prototype, but still had some major issues - although I don't think heat-related.
    That's interesting.

    Were all the valve filaments powered from the separate LT transformer?

    There are definite noise advantages in using separate filament and HT power transformers, although it's possible that this was done to keep the transformers slim enough to fit into 1U.

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  • ICBMICBM Frets: 71957
    edited May 2014
    jpfamps said:
    Were all the valve filaments powered from the separate LT transformer?

    There are definite noise advantages in using separate filament and HT power transformers, although it's possible that this was done to keep the transformers slim enough to fit into 1U.

    Yes, the HT PT was just that and the bias supply - the other one was for the split-rail LT and the filaments.

    The OT and the HT PT blew, at separate times, OT first. The owner got the maker (in Russia) to send a replacement OT, but had such a hassle with shipping and UK customs that when the PT later blew, rather than go through all that again I used a Marshall 20/20 PT - one of the few 1U-depth PTs available - which to get enough bias voltage (since it's a 6L6 amp and the PT is for an EL84 amp) I connected the spare Marshall LT windings in series with! Still not quite enough so I made up the difference with partial cathode bias. It actually all worked quite well in the end the amp has remained working fine since...

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • Danny1969Danny1969 Frets: 10357
    Clarky said:

    if you do take the Matrix route, go for the GT1000FX because it's a newer model than the GT800 and has the more valve-like feeling

    in the past I've used:

    Marshall 8008 [still have it and love it]

    Matrix GT1000FX [which is now my main power amp]

    Mesa Boogey Strategy 400 [huge, heavy, loud and awesome.. but you need a wheelbarrow to move it around]

    Marshall EL34 100/100 [which was surprisingly not much different from the 8008.. sure it was a superb, amp but I expected it to be so much better than the 8008.. and it just wasn't.. kinda popped the EL34 GAS bubble that I'd had for a year of so leading up to that moment]

    I had the 8008 @Clarky, then moved up to the little Marshall 2020 which I found to be a massive improvement. Then due to overheating the 2020 I moved up to the EL34 100 \ 100 which I still use now. This is all with a JMP-1 pre amp. What I hated about the 8008 was the harshness on low gain stuff, the valve powered amps seemed so much less harsh to me


    Pop the lid off and have a look inside. My 2020 was brought brand new in 2006 ish and the fan in mine drew air in from the side and blew it out the back. Drilling holes in the side of the rack case helped
    www.2020studios.co.uk 
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