I have a set of triode strapped 6V6 monoblocs that are basically copies of the Compact Amp. I would like to know if I can run a set of Cat5 wires terminated with RCA connectors from the 8 ohm output taps of my OPT to the input of another amp.
Is this crazy ? Will it work ? Limited bandwidth ? Will it provide enough drive ?
The amp(s) it may drive would be a Phase Linear 300 Series II , or a B&K EX-442.
Thanks for your help.
.....................................Blake
Is this crazy ? Will it work ? Limited bandwidth ? Will it provide enough drive ?
The amp(s) it may drive would be a Phase Linear 300 Series II , or a B&K EX-442.
Thanks for your help.
.....................................Blake
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You would probably blow up the other amp. You would be sending a high power, amplified signal into the low power inputs and it would do nothing good for that amp.
I am no expert, but that is what I think would be the result. Don't do it.
I am no expert, but that is what I think would be the result. Don't do it.
It'll work, but why you would want to beats me. The amplifier is probably going to be too noisy to perform adequately as a pre-amplifier, and you must load the outputs of the tube amplifier if you do not want to wreck the output transformers.. You will also have to pad down the signal at the output to prevent the possibility of excessively high levels being fed into your solid state amplifier.
What are you really trying to accomplish here? A properly designed tube pre will do a much better job without the risk of wrecking the solid state amplifier connected to it.
What are you really trying to accomplish here? A properly designed tube pre will do a much better job without the risk of wrecking the solid state amplifier connected to it.
I am making my second thru fourth set of tubelab simple se amps. My brother and a couple of friends liked them so much they wanted them also. But they wanted a volume control ( I didn't bother on mine, I'm using a tube pre amp)
And they wanted a Input selector.
No problem.
I am using two sets of inputs on my amp (RCA jacks) with an input selector in between them, before it goes to the amp circuit board the input signal will then go to another set of RCA jacks which will be the out put to a powered subwoofer.
Because the input impedance of the sub amp is ~25K ohms, it will be like it isn't even there as far as the driving source (pre amp or cd player ) nor will the tubelab simple se care either.
Paul
And they wanted a Input selector.
No problem.
I am using two sets of inputs on my amp (RCA jacks) with an input selector in between them, before it goes to the amp circuit board the input signal will then go to another set of RCA jacks which will be the out put to a powered subwoofer.
Because the input impedance of the sub amp is ~25K ohms, it will be like it isn't even there as far as the driving source (pre amp or cd player ) nor will the tubelab simple se care either.
Paul
"The amplifier is probably going to be too noisy to perform adequately as a pre-amplifier......"
What would ever give you that idea ? Triode strapped Push Pull 6V6's are well known for ultra low distortion. I'm not real sure what you are talking about here.
". . . . and you must load the outputs of the tube amplifier if you do not want to wreck the output transformers...."
Wouldn't the input of the SS amp I'm driving be the load ?
". . . .You will also have to pad down the signal at the output to prevent the possibility of excessively high levels being fed into your solid state amplifier."
The highest voltage I've measured across my speaker terminals with a DVM (I know , it's hardly accurate) is 6 volts or so. This is with the amp wide open . I hardly see where this will be a problem.
For some clarification, I run my DVD player through a passive volume control into my tube amp . My tube amp consists of the Triode section of a 6AN8 that drives a pair of triode strapped 6V6's in a Push Pull format , ALA the Compact Amplifier.
The input of the SS amp is in the hundreds of ohms, I'm pretty sure. I am NOT concerned with overdriving the amp, as any decent preamp is capable of that. My main concern is the mismatching of the OPT's 8 ohm tap and the input of the SS amp.
Any thoughts or concerns there ?
This is not going to be a long term setup. I just wanted to see how it would sound, and I wanted to listen to my system with more power than my 3-4 watt tube setup is capable of.
...........................Blake
What would ever give you that idea ? Triode strapped Push Pull 6V6's are well known for ultra low distortion. I'm not real sure what you are talking about here.
". . . . and you must load the outputs of the tube amplifier if you do not want to wreck the output transformers...."
Wouldn't the input of the SS amp I'm driving be the load ?
". . . .You will also have to pad down the signal at the output to prevent the possibility of excessively high levels being fed into your solid state amplifier."
The highest voltage I've measured across my speaker terminals with a DVM (I know , it's hardly accurate) is 6 volts or so. This is with the amp wide open . I hardly see where this will be a problem.
For some clarification, I run my DVD player through a passive volume control into my tube amp . My tube amp consists of the Triode section of a 6AN8 that drives a pair of triode strapped 6V6's in a Push Pull format , ALA the Compact Amplifier.
The input of the SS amp is in the hundreds of ohms, I'm pretty sure. I am NOT concerned with overdriving the amp, as any decent preamp is capable of that. My main concern is the mismatching of the OPT's 8 ohm tap and the input of the SS amp.
Any thoughts or concerns there ?
This is not going to be a long term setup. I just wanted to see how it would sound, and I wanted to listen to my system with more power than my 3-4 watt tube setup is capable of.
...........................Blake
Guess your idea of acceptable noise levels and mine don't quite jibe, and linearity and noise floor aren't nearly the same.
Also 6.0 Vrms is a lot to hit the input of a SS amplifier with - probably enough to drive your amplifier 14dB or more into hard clipping depending on its sensitivity.
As I was the only one who said it would work, and gave you some sound opinions based on 30+ yrs of experience in the field I'm more than a little puzzled that your reply to my comments would be a dismissive rant.. 😕
You should try it, and I will shut up and go elsewhere.
Also 6.0 Vrms is a lot to hit the input of a SS amplifier with - probably enough to drive your amplifier 14dB or more into hard clipping depending on its sensitivity.
As I was the only one who said it would work, and gave you some sound opinions based on 30+ yrs of experience in the field I'm more than a little puzzled that your reply to my comments would be a dismissive rant.. 😕
You should try it, and I will shut up and go elsewhere.
What we have here is, a failure to communicate . . .
Kevin,
I did not mean to rantingly dismiss your post. Sorry if it seemed so.
6 volts is the maximum voltage measured across speaker terminals with volume WIDE open. I understand that most SS amps need only 2 volts or so to reach max output.
As far as noise floor or linearity goes, can you tell me why they would suffer ? You don't need to get in depth, a basic answer will suffice. I was already concerned with the mismatch of the OPT to the input of the SS amp causing problems , so if there are other issues that I didn't consider, then I would appreciate you pointing them out/briefly explaining them.
I didn't intend for this to be a long term solution. If it would work halfway reasonably than I would try it and see how it fared for some high output jam sessions. Not looking for HIFI with this appication, just wanted to jam out and avoid any major snafu.
Thank you for your input.
...............Blake
Kevin,
I did not mean to rantingly dismiss your post. Sorry if it seemed so.
6 volts is the maximum voltage measured across speaker terminals with volume WIDE open. I understand that most SS amps need only 2 volts or so to reach max output.
As far as noise floor or linearity goes, can you tell me why they would suffer ? You don't need to get in depth, a basic answer will suffice. I was already concerned with the mismatch of the OPT to the input of the SS amp causing problems , so if there are other issues that I didn't consider, then I would appreciate you pointing them out/briefly explaining them.
I didn't intend for this to be a long term solution. If it would work halfway reasonably than I would try it and see how it fared for some high output jam sessions. Not looking for HIFI with this appication, just wanted to jam out and avoid any major snafu.
Thank you for your input.
...............Blake
not only but also...
the output of your Compact is 6Vrms @ 8 ohm load. What is it with no load (effectively what your power amp presents)? Now think about the consequence of that to both the Compact and your power amp.
Yep - any "decent" pre-amp may deliver upward of a few volts, but at what current capability? Remember your transformer output on your compact is a low z output - it has barely any impedance itself. Consider that when you do your "experiment"...
Best bet if you are still inclined to go ahead is to build a small voltage divider network with 10w resistors such that you pick up a 2Vp-p signal to take to your power amp. Connect it across your speaker outputs of the Compact and take the 2V signal to your power amp... This will ensure your OPTs in the Compact are sufficiently loaded and will also ensure you don't overdrive the power amp.
How will it sound? Probably not that great, but who knows. You want louder? Well, this is an oddly complex way to go about it. I presume your source (and passive volume control) can plug straight into the power amp after all...
Have fun.
the output of your Compact is 6Vrms @ 8 ohm load. What is it with no load (effectively what your power amp presents)? Now think about the consequence of that to both the Compact and your power amp.
Yep - any "decent" pre-amp may deliver upward of a few volts, but at what current capability? Remember your transformer output on your compact is a low z output - it has barely any impedance itself. Consider that when you do your "experiment"...
Best bet if you are still inclined to go ahead is to build a small voltage divider network with 10w resistors such that you pick up a 2Vp-p signal to take to your power amp. Connect it across your speaker outputs of the Compact and take the 2V signal to your power amp... This will ensure your OPTs in the Compact are sufficiently loaded and will also ensure you don't overdrive the power amp.
How will it sound? Probably not that great, but who knows. You want louder? Well, this is an oddly complex way to go about it. I presume your source (and passive volume control) can plug straight into the power amp after all...
Have fun.
Hi Blake,
Got your PM and thanks..
My comments were predicated on the fact that your power amplifier will produce some noise - noise which generally would not be audible or barely audible when connected to a pair of speakers. (Assuming that the amplifier is really quiet) I find generally that something less than 1mVrms at the power amplifier output with efficient speakers (100dBSpl/W/M) to be acceptably quiet under most circumstances. Now let's assume that your SS amplifier has 26dB of voltage gain (it might be more) - your rather reasonable 1mVrms of output noise is now 20mVrms at the output of the big SS amp and depending on the speakers you are using this could prove merely obtrusive or possibly intolerable particularly if there is any buzz component in the output.
Audible buzz is just harmonics of the line frequency. Rectifier ripple is nominally 120Hz (with 60Hz power) but this waveform is rich in largely even harmonics and a smattering of odd which extend to about 600Hz and which from experience even at low levels is quite audible. Add a small amount of 180Hz from magnetically coupled power transformer harmonics and you get the picture.
Oddly enough 60Hz hum (ground loops mostly) unless severe is not generally what people complain about, human hearing is substantially less sensitive to 60Hz than to 120Hz depending on Spl.
It is hard to put any specific numbers on it because I don't know what the efficiency of your speakers are or the voltage gain of your power amplifier.
One other thing that is important to mention is that directly connecting the tube amplifier to the SS amplifier means that its output is essentially unloaded - as far as it is concerned it is more or less open circuit, as the current drawn by the input circuitry of the power amplifier is small relative to what an 8 ohm speaker load requires. Under transient conditions (accident/line surge/etc) this can result in very large voltages being generated in the primary of the transformer due to flyback effects - the transformer can be destroyed under such conditions usually due to insulation failure.
The other thing that could happen is a catastrophic failure in the SS amplifier as it tries to act like a logic gate when its VAS saturates.. (Slow output stages sometimes cross conduct when the devices try to slew to follow the slope of the hard clipped driving waveform and can't - both devices are on simultaneously and this essentially crowbars the supply which usually wins out over the output transistors even when fuses are present.)
The two scenarios above are worst case, and with care are unlikely to happen, but I have seen both as a result of your exact intended usage scenario.
You can actually overcome this issue through the use of an attenuator/load across the output of the amplifier you wish to use as a pre-amplifier, the output noise will decrease in lock step with the signal level, the added attenuation forces you to drive the amplifier harder which results in a higher output level relative to the fixed noise sources in the amplifier, and this in fact results in an improved snr prior to your attenuator. Applying a load protects the opt, and the attenuation both improves effective snr and protects the SS power amplifier.
Before proceeding please check to see that the secondaries of your output transformers are grounded to chassis - this is mainly for safety. Should you experience a ground loop issue connecting the two amplifiers you should be able to use a single output ground as the ground connection point for both channels going to the SS amplifier. Hopefully one but not both of the amplifiers have AC safety grounds as this reduces the likelihood of ground loops. (Subject of another discussion..)
In this case a simple two resistor network combines both the required load to keep your output transformer(s) happy and provides the required attenuation. Using commonly available resistors you could attenuate by 6dB with two 4 ohm resistors in series (5W resistors should suffice) or for closer to 19 dB of attenuation try an 8 ohm resistor in series with a 1 ohm resistor. 5.6 and 2 ohms will give you about 11dB or so and might be a good choice. (Just the classic voltage attenuator realized with decent quality power resistors.) Use a good non-inductive wire wound for best results - the sand filled types IMO do not sound as good.
I would guess you probably don't need a whole lot of gain here, but might be looking for the ability to drive the input of the SS amplifier more effectively than your passive attenuator allows?
As long as you load the tube amplifier properly and attenuate the signals to the solid state amplifier so that you do not drive it into extremely hard clipping accidentally this should work fine. How it sounds depends heavily on the performance of the tube amplifier.
The cat5 cable should work fine as it is being driven by a very low source impedance of 2 ohms or less regardless of the ultimate attenuation you choose.
I hope I have clarified what I meant in my previous post, and on reflection my comments might have been a bit on the aggressive side.
FWIW Salas swears by the virtues of the 6V6 as a line stage device, so if you like this type you might want to check his thread on a 6V6 line stage or shoot him an email directly..
Hope this is useful.
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Thanks Kevin !
"In this case a simple two resistor network combines both the required load to keep your output transformer(s) happy and provides the required attenuation. Using commonly available resistors you could attenuate by 6dB with two 4 ohm resistors in series (5W resistors should suffice) or for closer to 19 dB of attenuation try an 8 ohm resistor in series with a 1 ohm resistor. 5.6 and 2 ohms will give you about 11dB or so and might be a good choice. (Just the classic voltage attenuator realized with decent quality power resistors.) Use a good non-inductive wire wound for best results - the sand filled types IMO do not sound as good. "
Forgive my ignorance, but why wouldn't I just use a single 8 ohm resistor ? Am I supposed to attach the series junction point to the input of the SS amp ?
FYI , yes, I am trying to drive the SS amp a bit harder than my passive volume control and DVD player will allow. I wouldn't mind a little tube flavoring in the mix , either 😉 .
I've previously read the post by Salas and found it interesting , to say the least. I'm a toob noob, limited in experience to 6V6 for output tubes and 6AN8 for phase splitter/driver. I've tried them in various formats, and am currently very much enjoying the Compact Amp format , using only the Triode section of the 6AN8 to drive the Triode strapped 6V6's. Just wish it was louder sometimes 😀
Perhaps I need to expand my horizons to larger output tubes. I'm just scared I won't like them as much as the Triode strapped 6V6's. I've read SO MUCH praise regarding them , and like them so very much that I'm being a scaredy cat about trying something new.
Here's a link to Fullrange Driver forum. A graph of the model preceeding my driver, the CR-12A. I am not sure, but I have been told the older model, CR-12AE , stands for Accordian Edge, while the newer version I have has a different surround and the A supposedly stands for AlNiCo.
Either way, the graph should be somewhat representative.
Fullrangedriver Forum / CalRad specs for CR-12AE and CR-8AE
Thanks for the help..........................Blake
"In this case a simple two resistor network combines both the required load to keep your output transformer(s) happy and provides the required attenuation. Using commonly available resistors you could attenuate by 6dB with two 4 ohm resistors in series (5W resistors should suffice) or for closer to 19 dB of attenuation try an 8 ohm resistor in series with a 1 ohm resistor. 5.6 and 2 ohms will give you about 11dB or so and might be a good choice. (Just the classic voltage attenuator realized with decent quality power resistors.) Use a good non-inductive wire wound for best results - the sand filled types IMO do not sound as good. "
Forgive my ignorance, but why wouldn't I just use a single 8 ohm resistor ? Am I supposed to attach the series junction point to the input of the SS amp ?
FYI , yes, I am trying to drive the SS amp a bit harder than my passive volume control and DVD player will allow. I wouldn't mind a little tube flavoring in the mix , either 😉 .
I've previously read the post by Salas and found it interesting , to say the least. I'm a toob noob, limited in experience to 6V6 for output tubes and 6AN8 for phase splitter/driver. I've tried them in various formats, and am currently very much enjoying the Compact Amp format , using only the Triode section of the 6AN8 to drive the Triode strapped 6V6's. Just wish it was louder sometimes 😀
Perhaps I need to expand my horizons to larger output tubes. I'm just scared I won't like them as much as the Triode strapped 6V6's. I've read SO MUCH praise regarding them , and like them so very much that I'm being a scaredy cat about trying something new.
Here's a link to Fullrange Driver forum. A graph of the model preceeding my driver, the CR-12A. I am not sure, but I have been told the older model, CR-12AE , stands for Accordian Edge, while the newer version I have has a different surround and the A supposedly stands for AlNiCo.
Either way, the graph should be somewhat representative.
Fullrangedriver Forum / CalRad specs for CR-12AE and CR-8AE
Thanks for the help..........................Blake
Thanks. Looks easy enuf. I'll give it a try this weekend. Gotta work at 6am tomorrow, so probably not gonna happen tonite.
.....................Blake
.....................Blake
Interesting thread.
I was asked to do this a couple of weeks ago and so gave it a try. It works OK.
Basically I did what was mentioned above with the voltage divider. You do want your tube amp to have a low impedance load, so choose 8 or 16 ohms. The input to the SS amp is going to be 10K or more.
Then figure out the voltage it takes to get your solid state amp to max power - or whatever point under that you wish to achieve. Let's say it's 2V RMS. Now you know how far you need to push the tube "preamp". With your 6V max output, you probably don't need to divide more than 1/2, maybe less.
The reason to do the dividing is to lower the noise floor coming out of your power preamp. Kevin has explained this well earlier. With your 6V max output, that means about 5 watts across 8 ohms. So 10 watt resistors will be just fine as your divider load (as mentioned earlier).
One thing you will have - a preamp with killer drive! Lots of voltage and a nice, low, low output impedance. How many other tube pres have an output impedance of ~10 ohms? =)
You just have to be a little careful about the noise floor is all. Go carefully, but have fun! Let us know how you like it.
I was asked to do this a couple of weeks ago and so gave it a try. It works OK.
Basically I did what was mentioned above with the voltage divider. You do want your tube amp to have a low impedance load, so choose 8 or 16 ohms. The input to the SS amp is going to be 10K or more.
Then figure out the voltage it takes to get your solid state amp to max power - or whatever point under that you wish to achieve. Let's say it's 2V RMS. Now you know how far you need to push the tube "preamp". With your 6V max output, you probably don't need to divide more than 1/2, maybe less.
The reason to do the dividing is to lower the noise floor coming out of your power preamp. Kevin has explained this well earlier. With your 6V max output, that means about 5 watts across 8 ohms. So 10 watt resistors will be just fine as your divider load (as mentioned earlier).
One thing you will have - a preamp with killer drive! Lots of voltage and a nice, low, low output impedance. How many other tube pres have an output impedance of ~10 ohms? =)
You just have to be a little careful about the noise floor is all. Go carefully, but have fun! Let us know how you like it.
All right guys, so it's been more than a couple weekends. Sorry for the delay, but you know how it is.
I just wired up the voltage dividing network today , with some 25W 8 ohm resistors I happened to have .
As was mentioned , noise floor was somewhat apparent (hum as soon as tube amp was turned on) when you were close to the speakers, but not really noticeable when in listening position.
Speaking of listening position , WOW ! You weren't kidding when you said it would have drive ! Bass is outstanding , everything else sounds quite good . I can barely wait until I have the amp running for a couple more days to "run it in" . I'm running a B&K EX-442 which is rated at 200wrms per channel. It has been dormant on my shelf for months. IDK if it is psycho acoustics or real, but it always seems to me that gear sounds better when it is left on or at least used daily.
The only problem I see with my current setup is that I am providing my tube amp with a 16 ohm load on an 8 ohm output tap. I know this should approximately double the load the tubes see, so I have about 13,200ohms load on my triode tied PP 6V6's (OPT is rated at 6600).
With a measured 9 volts or so at the driver , the spl is pretty loud ! I know this is only about 10 watts or so , but IDK that the drivers would like to see much more than that on an open baffle (they're rated at 20wrms and are from the mid '60s) . I only have the volume control turned up about 1/2 way at that point.
Thanks for the info , this is exactly what I wanted to achieve with this project.
Makes me drool for a set of Triode tied PP KT88's ! ! !
The downside to this project has only been the obvious "trasistor glare" (even though it has Mosfets in the output) that just isn't there with the tube amp. Hence the KT88 drool factor ! ! !
Thanks again guys !
.....................................Blake
I just wired up the voltage dividing network today , with some 25W 8 ohm resistors I happened to have .
As was mentioned , noise floor was somewhat apparent (hum as soon as tube amp was turned on) when you were close to the speakers, but not really noticeable when in listening position.
Speaking of listening position , WOW ! You weren't kidding when you said it would have drive ! Bass is outstanding , everything else sounds quite good . I can barely wait until I have the amp running for a couple more days to "run it in" . I'm running a B&K EX-442 which is rated at 200wrms per channel. It has been dormant on my shelf for months. IDK if it is psycho acoustics or real, but it always seems to me that gear sounds better when it is left on or at least used daily.
The only problem I see with my current setup is that I am providing my tube amp with a 16 ohm load on an 8 ohm output tap. I know this should approximately double the load the tubes see, so I have about 13,200ohms load on my triode tied PP 6V6's (OPT is rated at 6600).
With a measured 9 volts or so at the driver , the spl is pretty loud ! I know this is only about 10 watts or so , but IDK that the drivers would like to see much more than that on an open baffle (they're rated at 20wrms and are from the mid '60s) . I only have the volume control turned up about 1/2 way at that point.
Thanks for the info , this is exactly what I wanted to achieve with this project.
Makes me drool for a set of Triode tied PP KT88's ! ! !
The downside to this project has only been the obvious "trasistor glare" (even though it has Mosfets in the output) that just isn't there with the tube amp. Hence the KT88 drool factor ! ! !
Thanks again guys !
.....................................Blake
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