another "I need an amp recommendation" thread
Look,
I know you all have read these threads a thousand times. I know that because I searched and looked at a whole heap of them. The problem is that it is really hard to decide. eg: I saw the boozehound amp, thought , yeah this is great, easy to build for a relative beginner, built by others uses widely available tubes, but then saw it was 3WPC!
While it was very informative to read and spend an hour finding out about it, imagine repeating that exercise again and again! My head is starting to melt.
So please help! I need a power amp that will give me about 10-15WPC. It should be PP because I'll be using it with Quad ESLs and PP is meant to sound better. It should use easily available tubes eg 12AX7 and EL34, EL84 or KT88 for example. I'll be using it with a passive pre. Another example is that I looked at SYs red light amp - but the LED array is an added complication (for me!)! So I guess small parts count would help (eg the boozehound one looked great in this regard).
So I need a schematic and if there was a BOM to go with it that would be great. I can solder proficiently, I can make the chassis, I can buy the gear. If there was photo instructions along the was to help with transfer of schematic to real life, that would be great, but not a deal killer. It must sound good!!!!!!
Anyone out there who can offer help?
thanks,
Fran
Look,
I know you all have read these threads a thousand times. I know that because I searched and looked at a whole heap of them. The problem is that it is really hard to decide. eg: I saw the boozehound amp, thought , yeah this is great, easy to build for a relative beginner, built by others uses widely available tubes, but then saw it was 3WPC!
While it was very informative to read and spend an hour finding out about it, imagine repeating that exercise again and again! My head is starting to melt.
So please help! I need a power amp that will give me about 10-15WPC. It should be PP because I'll be using it with Quad ESLs and PP is meant to sound better. It should use easily available tubes eg 12AX7 and EL34, EL84 or KT88 for example. I'll be using it with a passive pre. Another example is that I looked at SYs red light amp - but the LED array is an added complication (for me!)! So I guess small parts count would help (eg the boozehound one looked great in this regard).
So I need a schematic and if there was a BOM to go with it that would be great. I can solder proficiently, I can make the chassis, I can buy the gear. If there was photo instructions along the was to help with transfer of schematic to real life, that would be great, but not a deal killer. It must sound good!!!!!!
Anyone out there who can offer help?
thanks,
Fran
Fran,
Check out "El Cheapo". It's simple and set up ultralinear "12" W. O/P tubes will yield the power you need. As drawn, 'AQ5s (6V6 "equivalent") are used. Changing the PP pair's cathode resistor allows the circuit to work with EL84s. The 12AT7/ECC81 is in production and good NOS is still affordable.
If you have the patience, read the entire lengthy thread.
Check out "El Cheapo". It's simple and set up ultralinear "12" W. O/P tubes will yield the power you need. As drawn, 'AQ5s (6V6 "equivalent") are used. Changing the PP pair's cathode resistor allows the circuit to work with EL84s. The 12AT7/ECC81 is in production and good NOS is still affordable.
If you have the patience, read the entire lengthy thread.
We built a 4 W variation of El Cheapo (triode wired Class A EL84 using a Scott LK48 donor) and it is superb. I look forward to hearing a RLD (the one headed to UKdiy is supposed to come up here... and we plan on doing a cross between El Cheapo (differential front-end) and RLD (LED biased output stage)
Both of these have about the same level of complexity... and if you want to make it simplier, UL wire the outputs (to eliminate the screen regs on the RLD) and add a hefty B- for the diff pair (eliminates the CCS in El Cheapo). They are both probably better with the SS (reg or CCS), but you can always add it later.
Except for the triode wired part Poinz's 6V6 is an example of the simple approach (for more power a UL OPT with screens tied to the UL tap thru a screen stopper resistor)
http://www.audiotropic.net/MachineUsersManual/mmUsersManual.html
(i consider EL84/6V6/6AQ5 to be roughly interchangable -- as Eli mentioned bias resistors change value)
dave
Both of these have about the same level of complexity... and if you want to make it simplier, UL wire the outputs (to eliminate the screen regs on the RLD) and add a hefty B- for the diff pair (eliminates the CCS in El Cheapo). They are both probably better with the SS (reg or CCS), but you can always add it later.
Except for the triode wired part Poinz's 6V6 is an example of the simple approach (for more power a UL OPT with screens tied to the UL tap thru a screen stopper resistor)
http://www.audiotropic.net/MachineUsersManual/mmUsersManual.html
(i consider EL84/6V6/6AQ5 to be roughly interchangable -- as Eli mentioned bias resistors change value)
dave
Hi Fran,
As you probably have read my posts in the tube section I highly recommend the "Baby Huey" as a simple build.
I can lend you the amp to listen to in your own system so you can judge. I don't know how it compares with "El Cheapo" - mine is built using ECL86 tubes recycled from Rogers Cadet.
It can also be built using ECL84 tubes - in either case it is a easy build.
Don't know if this helps?
JOhn
As you probably have read my posts in the tube section I highly recommend the "Baby Huey" as a simple build.
I can lend you the amp to listen to in your own system so you can judge. I don't know how it compares with "El Cheapo" - mine is built using ECL86 tubes recycled from Rogers Cadet.
It can also be built using ECL84 tubes - in either case it is a easy build.
Don't know if this helps?
JOhn
Well, I suppose today can mark the start date for this project!
I just bought some EL84s and some 9 pin tube sockets from ebay!
Looking at the schematics, I'm still undecided. Next I'm going to get a suitable PX. I'm kinda leaning towards SY's RLD but having John with a Baby Huey close by is very tempting. The only reason I haven't jumped on it is that my current amp is an ECL86/12AX7 job (and very good it is too), so I suppose I want something different.
A question for SY or RLD owners. I read in SY's article in Baz Hornemans mag that it is designed for 2V input to get a full 10W. Now I'm planning on using a passive pre with this as a power amp. My CDP puts out 2V, so do most things, but my phono stage I'd say would be a little lower (its a VSPS from RJM - see analogue section). I'm using ESL 57s as speakers. Will it be OK?
Fran
I just bought some EL84s and some 9 pin tube sockets from ebay!
Looking at the schematics, I'm still undecided. Next I'm going to get a suitable PX. I'm kinda leaning towards SY's RLD but having John with a Baby Huey close by is very tempting. The only reason I haven't jumped on it is that my current amp is an ECL86/12AX7 job (and very good it is too), so I suppose I want something different.
A question for SY or RLD owners. I read in SY's article in Baz Hornemans mag that it is designed for 2V input to get a full 10W. Now I'm planning on using a passive pre with this as a power amp. My CDP puts out 2V, so do most things, but my phono stage I'd say would be a little lower (its a VSPS from RJM - see analogue section). I'm using ESL 57s as speakers. Will it be OK?
Fran
SY, those ESLs are something aren't they! I've had wuite a few people with more expensive speakers walk away unhappy!
Anyway a Q for you,
Looking at using a PTx with a secondary of 230V. MJ reckons taht I should end up with about 285VDC after rectifiaction and regulation etc. Would this be enough to run the RLD?
(see cross post in transformer thread)
Fran
Anyway a Q for you,
Looking at using a PTx with a secondary of 230V. MJ reckons taht I should end up with about 285VDC after rectifiaction and regulation etc. Would this be enough to run the RLD?
(see cross post in transformer thread)
Fran
It's really a combination of things that does it, not just the LEDs. I'll have to look up the biasing of the ECL86 to see if it's suitable.
Anyway, 285V is probably adequate for the plates, but a bit low for the screens and their associated regulators. One option, at the expense of a bit of power, is to aim for 250V regulated on the screens and drop the LED strings from 7 in series to 6 in series. WAG, I'd say you're still good for 10-12W.
Anyway, 285V is probably adequate for the plates, but a bit low for the screens and their associated regulators. One option, at the expense of a bit of power, is to aim for 250V regulated on the screens and drop the LED strings from 7 in series to 6 in series. WAG, I'd say you're still good for 10-12W.
But why regulate the HT to the output stage? Your mains is actually 240V, and I don't believe you genuinely have a 240V to 230V transformer - far more likely that it's 240V to 240V. 240V rectified will be about 340V, and there's no problem in getting 320V (if you're careful) to the centre tap of the output transformer. Regulate the screens to 285V by all means (SY can confirm, but I don't think the change in voltage will be noticeable). All you now need is a 40V (ish) transformer to give a 50V supply that can be stacked on top of the 300V HT for the driver. Now you can go back to your EL84.
One thing to consider if you're going to try stacking a supply on top of the main HV rail- since the output stage is running AB, the output tube plate rails droop a bit when the amp is driven hard. With the phase-splitter and voltage amp power connections tied together (as EC8010 suggested during the design phase of this project), motorboating will probably be avoided, but I think there's advantage to having the driver stage rail not move around. Thus the separate transformer in my version.
285V is probably OK for the screens, but it needs some adjustment range. As one constructor found out, if your EL84s are at the low end of emission, the idle current will be too low even with the screen run up to the 300V max rating. I don't mid abusing the plates a bit, but I'm wary of overdoing screen ratings. As mentioned before, the workaround is to remove one LED from each series string, which in effect lowers the grid bias by 1.7V.
285V is probably OK for the screens, but it needs some adjustment range. As one constructor found out, if your EL84s are at the low end of emission, the idle current will be too low even with the screen run up to the 300V max rating. I don't mid abusing the plates a bit, but I'm wary of overdoing screen ratings. As mentioned before, the workaround is to remove one LED from each series string, which in effect lowers the grid bias by 1.7V.
John,
I know I could mod the ECL 86 amp that I have, but its my reference and I like it ..... a lot. So I don't want to mess with it. Plus its a PCB affair so not quite as easy.
Thanks to SY and ECC8010 for the suggestions, I think I'll have a crack at using the 285 (or maybe higher depending). I have often measured incoming mains in the range 220 to 240, so its not always 240. But as you say, yes the transformer is a standard RScomponents job 230pri - 230sec.
I have yet to sit down and really study the article in hornemans mag, (temp printer probs here). So if necessary I can get 2 transformers for the job. Theres pletny with 55-0-55 secondaries that are easily avaialble.
Thanks again,
Fran
I know I could mod the ECL 86 amp that I have, but its my reference and I like it ..... a lot. So I don't want to mess with it. Plus its a PCB affair so not quite as easy.
Thanks to SY and ECC8010 for the suggestions, I think I'll have a crack at using the 285 (or maybe higher depending). I have often measured incoming mains in the range 220 to 240, so its not always 240. But as you say, yes the transformer is a standard RScomponents job 230pri - 230sec.
I have yet to sit down and really study the article in hornemans mag, (temp printer probs here). So if necessary I can get 2 transformers for the job. Theres pletny with 55-0-55 secondaries that are easily avaialble.
Thanks again,
Fran
Hi again,
what would you guys think of a deal like this:
dynaco clone Tx
All in cost would be $253 incl shipping etc. Might have to deal with customs.
If I go the separate route for the power transformers (which I'm happy to, total cost approx $100) where can I lay hands on output transformers - is triode electronics a good place?
Fran
what would you guys think of a deal like this:
dynaco clone Tx
All in cost would be $253 incl shipping etc. Might have to deal with customs.
If I go the separate route for the power transformers (which I'm happy to, total cost approx $100) where can I lay hands on output transformers - is triode electronics a good place?
Fran
woodturner-fran said:
You will certainly have to deal with Customs. And pay the shipper for the privilege of them paying Customs.
Those look like toroidal output transformers. Expect poor LF response unless anode currents are matched to within 1mA at all times.
All in all, not a deal I would consider.
OK,
advice taken.
What about here:
triode electronics output Tx
All in all I think I'll go the route of the separate transformers for the power supply. It may lead to extra space being needed but for a new fella, I think it might make life a bit simpler.
Now output Tx are next... hence the above link!
thanks again,
Fran
advice taken.
What about here:
triode electronics output Tx
All in all I think I'll go the route of the separate transformers for the power supply. It may lead to extra space being needed but for a new fella, I think it might make life a bit simpler.
Now output Tx are next... hence the above link!
thanks again,
Fran
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