replace EL34 with EL37 !?

athode · 24th December 2011, 08:04 PM

Hi! I want to know if I can replace the EL34 output tube on my eico HF-89 with EL37 tube and if I need to do some modification on resistor value on the circuit.

v4lve lover · 24th December 2011, 08:40 PM

why would you EL37 are pretty rare classics . simmilair to 6l6
el34 can be had much easier

athode · 24th December 2011, 08:54 PM

It's because I have 4 mullard EL37 and I want to hear it!

kevinkr · 24th December 2011, 09:24 PM

You may need to reduce the plate voltage significantly, and the grid bias voltage probably needs to be increased into 6L6 territory, -40V or more.

The Mullard EL37 is reputed to be an excellent performer, and I can understand your curiosity, just make sure that you are operating them inside of acceptable plate dissipation, voltage and current values. Since they are yours obviously you can do anything you want with them, and were I you I would try them and if I liked the results would use them. Museum pieces are fine, but...

vinylkid58 · 24th December 2011, 09:33 PM

Quote:

Originally Posted by athode

It's because I have 4 mullard EL37 and I want to hear it!

Luckeeeee!

jeff

athode · 24th December 2011, 09:50 PM

With the original configuration of the eico HF-89 (EL34) plate voltage is 487v and bias voltage is -46v

DavesNotHere · 04:06 AM

ok, swap the 15k and 10 resistor in bias

change B+ supply to full wave bridge type

Bias at approx -15V @ 275 V B+
-13.5@ 250 VB+

depends where the B+ lies when you change the power.

SY · 25th December 2011, 10:22 AM

I did the swap in an HF87 (which had previously been modified for fixed bias). The EL37s performed spectacularly well. 45 watts at midband.

h00hbt · 25th December 2011, 10:42 AM

Quote:

Originally Posted by DavesNotHere

ok, swap the 15k and 10 resistor in bias

change B+ supply to full wave bridge type

Bias at approx -15V @ 275 V B+
-13.5@ 250 VB+

depends where the B+ lies when you change the power.

Just curious, what would the primary of the OPT be?

Cheers

briansune · 25th December 2011, 02:42 PM

Does EL34 really same as 6L6 in plate supply and the grids cause, i am still thinking to change El34 into 6L6> In case i had read the data sheet from the wed and i saw the class a voltage supply is really the same but the output power is little bit different> Could any one taught me < Thanks A Lot~

24th December 2011, 08:04 PM	#1
athode diyAudio Member Join Date: Dec 2011 Location: Terrebonne,QC	replace EL34 with EL37 !? Hi! I want to know if I can replace the EL34 output tube on my eico HF-89 with EL37 tube and if I need to do some modification on resistor value on the circuit.

24th December 2011, 09:24 PM	#4
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	You may need to reduce the plate voltage significantly, and the grid bias voltage probably needs to be increased into 6L6 territory, -40V or more. The Mullard EL37 is reputed to be an excellent performer, and I can understand your curiosity, just make sure that you are operating them inside of acceptable plate dissipation, voltage and current values. Since they are yours obviously you can do anything you want with them, and were I you I would try them and if I liked the results would use them. Museum pieces are fine, but... __________________ www.kta-hifi.net

25th December 2011, 10:22 AM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I did the swap in an HF87 (which had previously been modified for fixed bias). The EL37s performed spectacularly well. 45 watts at midband. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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24th December 2011, 08:40 PM	#2
v4lve lover diyAudio Member Join Date: Aug 2010	why would you EL37 are pretty rare classics . simmilair to 6l6 el34 can be had much easier

24th December 2011, 08:54 PM	#3
athode diyAudio Member Join Date: Dec 2011 Location: Terrebonne,QC	It's because I have 4 mullard EL37 and I want to hear it!

24th December 2011, 09:50 PM	#6
athode diyAudio Member Join Date: Dec 2011 Location: Terrebonne,QC	With the original configuration of the eico HF-89 (EL34) plate voltage is 487v and bias voltage is -46v

25th December 2011, 02:42 PM	#10
briansune diyAudio Member Join Date: Sep 2011	Does EL34 really same as 6L6 in plate supply and the grids cause, i am still thinking to change El34 into 6L6> In case i had read the data sheet from the wed and i saw the class a voltage supply is really the same but the output power is little bit different> Could any one taught me < Thanks A Lot~

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